Method of producing prepreg for printed wiring boards, glass fiber material treated with silicone oligomer, and laminate for printed wiring boards

ABSTRACT

Printed wiring boards improved in the drilling processability and insulation properties are produced either by treating the surfaces of base materials or inorganic fillers with silicone oligomers having specified structures, particularly, a three-dimensionally crosslinked silicone oligomer, or by using resin varnish prepared by compounding such a silicone oligomer with a resin varnish for impregnation of the base materials, or by dipping the inorganic fillers in a solution of such a silicone oligomer for surface treatment and then directly compounding resin materials with the solution.

[0001] This application is a Divisional application of U.S. Ser. No.08/981,570, filed Dec. 23, 1997, which is an application filed under 35USC §371 of PCT International Application No. PCT/JP98/01708, filed Jun.20, 1996, and amended on Mar. 27, 1997.

BACKGROUND

[0002] The present invention relates to the production of prepregs andresin varnishes useful for the production of printed wiring boardsincluding multilayer printed wiring boards. The present invention alsorelates to resin compositions useful for the production of printedwiring boards. The present invention further relates to laminates forprinted wiring boards which are produced by using the prepregs or theresin varnishes.

[0003] As electronic instruments have been miniaturized and improved inperformance, the mounting density of laminates for printed wiring boardshas been increased by making the laminates thinner and more multilayeredand by reducing the diameter and hole pitch of through holes. Thus, therequirements of laminates for heat resistance, drilling processabilityand insulation properties are becoming more strict.

[0004] Laminates are generally produced by impregnating a base materialwith a resin varnish and drying to form a prepreg, and superposing adesired number of sheets of the prepreg on each other with a metal foilsuperposed on one or both sides, and heating and pressing with aparallel heat machine. Multilayer printed wiring boards are generallyproduced by superposing prepregs on each side of an inner printed wiringboard produced by circuit-patterning a double-sided metal-clad laminate,and then superposing metal foil on the prepregs, and then bonding thesuperposed composite with heat and pressure between a parallel heatmachine.

[0005] To improve the heat resistance and insulation properties, theimprovements in the properties of the cured resins in the laminates havewidely been tried, for example, by increasing the Tg (glass transitiontemperature) of the resins. Such improvements in resin properties,however, became insufficient to satisfy the required properties.

[0006] In parallel with the improvements in the resin properties, along-standing investigation has been made to increase the basematerial/resin interfacial adhesion. Interface control is a veryimportant technique since the degree of interfacial adhesion directlyinfluences the resistance against heat and moisture, drillingprocessability, insulation properties and electrolytic corrosionresistance of laminates.

[0007] Another means is the addition of inorganic fillers. Inorganicfillers are used not only as extenders but also for improvingdimensional stability and resistance against moisture and heat, andselective use of specific fillers has recently been investigated toattain excellent properties, such as high dielectric constant, efficientradiation and high strength. However, fillers added to resin varnishesprecipitate slowly and should be dispersed again by stirring or the likeat the time of coating. When the precipitation is considerable, theprecipitated fillers cohere on the bottom of containers, and becomedifficult to disperse by stirring alone. During the production ofprepregs, fillers also precipitate in apparatuses where varnishes stay,for example, in varnish tanks and impregnating tanks, and graduallyadhere to rolls, etc. This deteriorates the appearance of prepregsconsiderably. In laminates, the inhomogeneously dispersed fillersdecrease the interfacial adhesion between base materials and resins orbetween the fillers and resins, thereby deteriorating the drillingprocessability and insulation properties.

[0008] A general method of improving the base material/resin interfacialadhesion is the pretreatment of base materials, such as glass wovenfabric, with surface treating agents, such as coupling agents. Prepregsare produced by impregnating a surface-treated base material with aresin varnish and then drying to semi-cure the resin. During the dryingstep, the reaction of the surface treating agent on the surface of thebase material with the resin proceeds to some degree, and furtherproceeds during the following heating step for forming laminates ormultilayer printed wiring boards, to increase the adhesion between thebase material and the resin. A known method of further increasing theadhesion is to improve the reactivity of surface treating agents withresins by varying the number and kinds of the organic functional groupson the conventional surface treating agents, such as silane couplingagents (Japanese Patent Application Unexamined Publication No. 63-230729and Japanese Patent Application Examined Publication No. 62-40368). Theimproved reactivity with resins, however, merely gives a rigid and thinlayer on the interfaces, and cannot decrease the residual stress set upon the interfaces and cannot improve the adhesion remarkably.

[0009] Another method of improvements, including a reduction of theresidual stress on interfaces, is the use of surface treating agentstogether with long chain polysiloxanes which reduce such stress(Japanese Patent Application Unexamined Publication Nos. 3-62845 and3-287869). The method, however, is far from effective in increasing theinterfacial adhesion since the reactivity of surface treating agentswith long chain polysiloxanes is very poor under usual treatingconditions, long chain polysiloxane have no alkoxyl groups reactive tobase materials, and the hydrophobic groups, such as methyl groups, onlong chain polysiloxanes disturb the impregnation of base materials withthe long chain polysiloxanes.

[0010] It has also been tried to improve the dispersibility of fillersby using fillers treated with surface treating agents, such as couplingagents. However, commercially available surface-treated fillers areexpensive, and the kinds thereof are too little to select a properfiller for each of various resin blends. For further improvements infunctions, the amount of fillers blended in resins is now increasing. Asthe amount of fillers increases, the above-described precipitation andadhesion to rolls become more considerable, requiring furtherimprovements in dispersibility and thixotropy. The conventionaltreatments with coupling agents cannot satisfy such requirements.

[0011] In addition, the treatments of fillers with surface treatingagents are generally performed by dipping or spraying using dilutedsolutions of the surface treating agents, followed by drying with heat.The drying step raises two problems, namely, the formation of physicallyadsorbed layer of oligomerized coupling agents on the filler surfaces,and the cohesion of fillers, which necessitates grinding at the time ofblending with resin varnishes. Such grinding roughens the surfacetreating agent layers on fillers. The physically adsorbed layers and theuneven layers of surface treating agents decrease the interfacialadhesion in laminates.

[0012] It is also proposed in Japanese Patent Application UnexaminedPublication No. 61-272243 to add coupling agents directly into resinvarnishes under preparation. The layers formed from commercial couplingagents are also too rigid and thin to improve the interfacial adhesionbetween base material/resin. On the other hand, this method somewhatprevents the cohesion of fillers because of the high viscosity of theresin varnishes containing resins. From the viewpoint of thefiller/resin interfacial adhesion, the coupling agents cannot alignselectively and uniformly on the filler surfaces, and cannot bond thefillers and resins sufficiently.

[0013]FIG. 1 shows a schematic view illustrating an ideal state of thesurfaces of base materials or fillers which are treated withconventional silane-coupling agents. Chemically adsorbed silicone chains2 (silicone chains adsorbed via chemical bonding with base materials orfillers) form a layer of a certain thickness on the surface of a basematerial or inorganic filler 1, and improve the adhesion to a resinlayer 4. The layer of chemically adsorbed silicone chains 2 bearsphysically adsorbed silicone chains 3 (silicone chains having nochemical bonds with the base material or filler) thereon. However, it iscommonly recognized that the state as shown in FIG. 2 is the actualstate made by industrial surface treatments of base materials orfillers, which are performed in a short time. That is, even thechemically adsorbed silicone chains 2 do not cover the surface of thebase material or filler 1 uniformly, and there are many physicallyadsorbed silicone chains 3, which are easily eluted into the resin layer4. Such a defective chemically adsorbed layer cannot fully exhibit itsbonding function. The physically adsorbed layer may inhomogenize andweaken the resin which is cured near the interface, and may ratherdecrease the adhesion.

[0014] In Japanese Patent Application Unexamined Publication No.1-204953 is proposed to solve such problems by treating inorganicfillers with a linear polysiloxane which has both trialkoxyl groupsreactive to inorganic fillers and organic functional groups reactive toresins. As shown in FIG. 3, chemically adsorbed linearly longpolysiloxane chains 6 tend to lie on the filler surface due to thealignment of hydrophobic groups, such as methyl groups, and hardlypenetrate into the resin layer 4. Also such long chains bond to theinorganic filler surface at several sites per molecule and tend to forma rigid layer. Even if penetrated into the resin, the siloxane chainsare surrounded by the resin, and the decrease in the interfacial stressdoes not correspond to the chain length. Further, the physicallyadsorbed long polysiloxane chains 7 easily form large cyclic chains 5,which tend to deteriorate the properties of cured resins.

DISCLOSURE OF INVENTION

[0015] The object of the present invention is to solve theabove-described problems in the prior arts by providing novel means forimproving the interfacial adhesion between base materials or inorganicfillers with resins, thereby enabling the production of laminates andmultilayer printed wiring boards which are excellent in drillingprocessability and insulation properties.

[0016] The inventors found that the above-described problems can besolved by using, as surface treating agents for base materials andinorganic fillers, a silicone oligomer having functional groups reactiveto the hydroxyl groups which are present structurally or by moistureabsorption on the surfaces of base materials and fillers, or by usingnovel method for producing resin varnishes containing inorganic fillerstreated with such a silicone oligomer, and have consequently completedthe present invention.

[0017] That is, the present invention provides a method of producing aprepreg for printed wiring boards, comprising treating a base materialwith a silicone oligomer, impregnating the treated base material with aresin varnish, and drying the impregnated base material, the siliconeoligomer containing at least one kind of siloxane units selected fromthe group consisting of trifunctional siloxane units (RSiO_(3/2)) andtetrafunctional siloxane units (SiO_(4/2)), having a polymerizationdegree of 2 to 70 and having at least one functional end group reactiveto a hydroxyl group, each R being an organic group, and the R groups inthe silicone oligomer being identical with or different from oneanother.

[0018] The present invention also provides a laminate for printed wiringboards (hereinafter, it may be called “laminate (a)”), which is producedby superposing two or more sheets of the above-described prepreg, with ametal foil superposed on one or both sides of the superposed sheets ofthe prepreg, to form a superposed composite, and then bonding thesuperposed composite with heat and pressure.

[0019] The present invention further provides a method of producing aresin varnish for printed wiring boards comprising dipping an inorganicfiller in a treating liquid for surface treatment, and then compoundinga resin material directly with the treating liquid containing thetreated inorganic filler, wherein the treating liquid comprises asilicone oligomer dissolved in a solvent, and the silicone oligomercontains at least one kind of siloxane units selected from trifunctionalsiloxane units (RSiO_(3/2)) and tetrafunctional siloxane units(SiO_(4/2)), wherein each R is an organic group and the organic groups Rin the silicone oligomer are identical with or different from oneanother, has a polymerization degree of 2 to 70, and has at least onefunctional end group reactive to a hydroxyl group.

[0020] The present invention also provides a laminate for printed wiringboards (hereinafter, it may be called “laminate (b)”), which is producedby impregnating a base material with the resin varnish produced by theabove described method, drying the impregnated base material to form aprepreg, superposing two or more sheets of the prepreg, with a metalfoil superposed on one or both sides of the superposed sheets of theprepreg, to form a superposed composite, and then bonding the superposedcomposite with heat and pressure.

[0021] The present invention further provides a resin composition forprinted wiring boards (hereinafter, it may be called “resin compositionfor printed wiring boards (A)” or “resin composition (A)”) comprising aresin material and the above-described silicone oligomer.

[0022] The present invention also provides a laminate for printed wiringboards (hereinafter, it may be called “laminate (c)”), which is producedby impregnating a base material with the resin composition (A), dryingthe impregnated base material to form a prepreg, superposing two or moresheets of the prepreg, with a metal foil superposed on one or both sidesof the superposed sheets of the prepreg, to form a superposed composite,and then bonding the superposed composite with heat and pressure.

[0023] The present invention further provides a resin composition forprinted wiring boards (hereinafter, it may be called “resin compositionfor printed wiring boards (B)” or “resin composition (B)”) comprising aresin material and an inorganic filler treated with a silicone oligomerwhich contains at least one kind of siloxane units selected fromtrifunctional siloxane units (RSiO_(3/2)) and tetrafunctional siloxaneunits (SiO_(4/2)), wherein each R is an organic group and the organicgroups R in the silicone oligomer are identical with or different fromone another, has a polymerization degree of 2 to 70, and has at leastone functional end group reactive to a hydroxyl group.

[0024] The present invention also provides a laminate for printed wiringboards (hereinafter, it may be called “laminate (d)”), which is producedby impregnating a base material with the resin composition (B), dryingthe impregnated base material to form a prepreg, superposing two or moresheets of the prepreg, with a metal foil superposed on one or both sidesof the superposed sheets of the prepreg, to form a superposed composite,and then bonding the superposed composite with heat and pressure.

BRIEF DESCRIPTION OF DRAWINGS

[0025] FIGS. 1 to 4 are schematic views illustrating the states of theinterfaces between resins and base materials or inorganic fillerstreated with surface treating agents.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Method of Producing prepregs for printed wiring boards

[0027] In the method of producing prepregs for printed wiring boardsaccording to the present invention, first a base material is treatedwith a silicone oligomer having at least one functional end groupreactive to a hydroxyl group.

[0028] Base materials which may be used in the present invention may bethose commonly used for the production of metal-clad laminates ormultilayer printed wiring boards, and are generally fiber basematerials, including woven fabrics and non-woven fabrics. Non-limitingexamples of the fiber base materials are inorganic fibers, such as glassfiber, alumina fiber, asbestos fiber, boron fiber, silica alumina glassfiber, silica glass fiber, tyranno fiber, silicon carbide fiber, siliconnitride fiber, zirconia fiber and carbon fiber, organic fibers, such asaramid fiber, polyetheretherketone fiber, polyetherimide fiber,polyethersulfone fiber and cellulose fiber, and mixed fibers thereof,and the particularly preferred example is a woven fabric of glassfibers.

[0029] The surface state of the base materials to be treated with thesilicone oligomers is not limited, and may have been pretreated withconventional surface treating agents, such as silane coupling agents. Itis generally preferable to use base materials which have not beentreated with other conventional surface treating agents and have ontheir surfaces hydroxyl groups which react with the silicone oligomer.

[0030] The silicone oligomers which may be used in the present inventionare not limited in molecular weight and structure so far as they have atleast one functional end group reactive to the hydroxyl groups on basematerials. Preferred examples of the functional end groups reactive tothe hydroxyl groups on the surfaces of base materials are alkoxyl groupsof one or two carbon atoms or silanol group.

[0031] Preferred silicone oligomers contain at least one kind ofsiloxane units selected from trifunctional siloxane units (RSiO_(3/2), Rbeing an organic group, for example, an alkyl group of one or two carbonatoms, such as methyl or ethyl, an aryl group of 6 to 12 carbon atoms,such as phenyl, and vinyl, and the R groups in the silicone oligomerbeing identical with or different from one another) and tetrafunctionalsiloxane units (SiO_(4/2)), and, optionally, difunctional siloxane units(R₂SiO_(2/2)), and have a polymerization degree of 2 to 70 (conversionfrom weight average molecular weight determined by GPC). Siliconeoligomers of polymerization degrees of higher than 70 may cause uneventreatment to decrease heat resistance.

[0032] The difunctional, trifunctional and tetrafunctional siloxaneunits represented, respectively, by R₂SiO_(2/2), RSiO_(3/2) andSiO_(4/2) have the following structures:

[0033] Preferred silicone oligomers are three-dimensionally crosslinkedoligomers, which comprise at least one kind of siloxane units selectedfrom difunctional siloxane units, trifunctional siloxane units andtetrafunctional siloxane units and contain at least one kind of siloxaneunits selected from trifunctional siloxane units and tetrafunctionalsiloxane units. That is, the preferred silicone oligomers comprise onlytrifunctional siloxane units, or only tetrafunctional siloxane units, ordifunctional siloxane units and trifunctional siloxane units, ordifunctional siloxane units and tetrafunctional siloxane units, ortrifunctional siloxane units and tetrafunctional siloxane units, ordifunctional siloxane units, trifunctional siloxane units andtetrafunctional siloxane units. Further, tetrafunctional siloxane unitsare preferably 15 mol % or more, more preferably 20 to 60 mol %, basedon total siloxane units. To coat the surfaces of base materials with ahighly three-dimensionally crosslinked layer, it is preferable to usesilicone oligomers containing trifunctional siloxane :units and/ortetrafunctional siloxane units preferably and having a polymerizationdegree of 6 to 70, more preferably 10 to 50. Such silicone oligomers aresynthesized, for example, by polycondensing one or more kinds of chloroor alkoxysilanes corresponding to the desired siloxane units, in thepresence of water and acid catalysts. The polycondensation is carriedout to such a degree that the resulting silicone oligomers are notgelified before surface treatment, by varying or controlling thereaction temperature, the reaction time, the compositions of theoligomers, and the kind and amount of the catalysts. Suitable catalystsare, for example, acetic acid, hydrochloric acid, maleic acid andphosphoric acid.

[0034] Although the method of treating base materials, including thecomposition of the treating liquid containing the silicone oligomers andthe treating conditions, is not particularly limited, the adhesionamount of the silicone oligomers on base materials is preferably 0.01 to5% by weight, more preferably 0.05 to 2.00% by weight. Herein, theadhesion amount of surface treating agents means the percentage of theweight of the surface treating agents adhering to base materials orinorganic fillers, based on the weight of the base materials orinorganic fillers. An adhesion amount of less than 0.01% by weight maybe ineffective in improving interfacial adhesion, and an adhesion amountof more than 5% by weight may deteriorate heat resistance.

[0035] The treating liquid used for treating base materials may contain,in addition to the silicone oligomers, solvents and additives includingcoupling agents, such as silane coupling agents and titanate couplingagents. Examples of the silane coupling agents which may be used includeepoxysilane coupling agents, such as γ-glycidoxypropyltrimethoxysilane,aminosilane coupling agents, such asN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyl-trimethoxysilaney•hydrochloride,cationic silane coupling agents, vinylsilane coupling agents,acrylsilane coupling agents, mercaptosilane coupling agents, andmixtures thereof. An example of the titanate coupling agents isisopropyltris(dioctylpyrophosphate) titanate. The adhesion amounts ofthese coupling agents are not particularly limited. Thesurface-treatment of base materials with silane coupling agents ortitanate coupling agents may also be carried out before or after thetreatment with the silicone oligomers. In such cases, the adhesionamount of coupling agents is preferably 5% by weight or less, morepreferably 0.01 to 5% by weight. To stabilize these components, thetreating liquid may contain acids, such as acetic acid, phosphoric acid,maleic acid, hydrochloric acid and sulfuric acid. The amount of theacids is not particularly limited, and is generally such that thetreating liquid is adjusted to a Ph of 3 to 6.

[0036] Although the method of treating base materials, including thecomposition of the treating liquid containing the silicone oligomers andthe treating conditions, is not particularly limited, it is desirable todip base materials in a treating liquid containing silicone oligomersdissolved in solvents, followed by drying at 50 to 200° C., preferably80 to 150° C., for 5 to 60 minutes, preferably 10 to 30 minutes. Incases where solvents are used, the amount of the solvents are notparticularly limited, but are desirably such that the concentration ofthe solids, such as silicone oligomers, is 0.01 to 50% by weight,preferably 0.05 to 10% by weight. The solvents are not particularlylimited, and preferred examples include water, alcohols, such asmethanol and ethanol, and ketones, such as methyl ethyl ketone andmethyl isobutyl ketone.

[0037] The base materials treated with the silicone oligomer are thenimpregnated with resin varnishes and dried, to give prepregs.

[0038] Resin varnishes generally contain resins, or resins and curingagents therefor, as essential components. Resin varnishes, according todemands, may further contain, for example, solvents, cure acceleratorsfor accelerating the reactions of the resins and the curing agents, andinorganic fillers.

[0039] Resins which may be used in the present invention for theproduction of prepregs are not particularly limited, and some examplesinclude epoxy resin, polyimide resin, triazine resin, phenolic resin,melamine resin and modified resins therefrom. These resins preferablyhave a weight average molecular weight of 200 to 100,000, morepreferably 200 to 10,000. Preferred epoxy resins have an epoxyequivalent weight of 100 to 5,000, more preferably 150 to 600. Theseresins may be used individually or as a mixture of two or more.

[0040] Curing agents may be selected from various known ones, and whenepoxy resins are used as resins, for example, dicyandiamide,diaminodiphenylmethane, diaminodiphenylsulfone, phthalic anhydride,pyromellitic anhydride, and polyfunctional phenols, such as phenolnovolac and cresol novolac, are suitable. Cure accelerators are notparticularly limited and are, for example, imidazole compounds, organicphosphorus compounds, tertiary amines and quaternary ammonium salts, andthese may be used individually or as a mixture of two or more.

[0041] The amounts of the curing agents and cure accelerators depend onthe kinds and combinations of the resins and curing agents, or the like.The amount of curing agents is generally 0.1 to 200 parts by weight,preferably 3.0 to 100 parts by weight, per 100 parts by weight of theresins, and the amount of cure accelerators is generally 0.01 to 10.0parts by weight, preferably 0.1 to 5.0 parts by weight, per 100 parts byweight of the resins.

[0042] Solvents which may be used are not limited, and some examplesinclude alcohols, such as methanol and ethanol, ethers, such as ethyleneglycol monomethyl ether, ketones, such as acetone, methyl ethyl ketoneand methyl isobutyl ketone, amides, such as N,N-dimethylformamide,aromatic hydrocarbons, such as toluene and xylene, esters, such as ethylacetate, and nitrites. These may be used individually or as a solventmixture of two or more.

[0043] Inorganic fillers which may be used are not limited, and someexamples include calcium carbonate, alumina, titanium oxide, mica,aluminum carbonate, aluminum hydroxide, magnesium silicate, aluminumsilicate, clay, such as calcined clay, talc, silica, glass short fiberand various whiskers, such as aluminum borate whisker and siliconcarbide whisker. These may be used individually or as a mixture of twoor more. The amount of inorganic fillers is not limited, and isdesirable 1.0 to 500 parts by weight, preferably 10 to 100 parts byweight, per 100 parts by weight of the resins. The inorganic fillers arenot particularly limited in shape and particle size, and the particlesize is desirably 0.01 to 50 μm, preferably 0.1 to 15.0 μm.

[0044] The surface-treated base materials are impregnated with a resinvarnish which is a blend of the above-described components, by dipping,coating, spraying or the like, and then dried to give prepregs forprinted wiring boards. Although the drying temperature and time dependon the composition of the resin varnish, the drying step is generallyperformed at a temperature of 80 to 200° C., preferably 100 to 180° C.,which is not lower than the temperature at which the solvents, if any,can evaporate, for 3 to 30 minutes, preferably 5 to 15 minutes.

[0045] According to the present invention, prepregs are produced byusing base materials which have been previously treated with a siliconeoligomer having at least one functional end group reactive to thehydroxyl group present on the surfaces of base materials. In laminatesor multilayer printed wiring boards produced by using the prepregs, thesilicone oligomer works as a cushion between the base materials andcured resins, while the conventional coupling agents including silanecoupling agents form a rigid and thin layer. Thus the silicone oligomerlayer relieves the contortion on the interface between the basematerials and the cured resins, to allow the resins to exhibit theirexcellent adhering properties.

[0046] Laminates (a) for printed wiring boards

[0047] The laminate (a) of the present invention is useful for theproduction of printed wiring boards and is produced by superposing twoor more sheets of a prepreg produced as above, with a metal foilsuperposed on one or both sides of the superposed sheets of the prepreg,to form a superposed composite, and then bonding the superposedcomposite with heat and pressure.

[0048] By heating and pressing the superposed prepreg, with metal foilsuperposed on one side, a single-sided metal-clad laminate is produced.By heating and pressing the superposed prepreg, with metal foilsuperposed on both sides, a double-sided metal-clad laminate isproduced. The metal foil may be selected without limitation from thosecommonly used for the production of printed wiring boards, and copperfoil is generally suitable. In general, the bonding is suitablyperformed by heating at a temperature of 150 to 200° C. for 30 to 150minutes with pressing at 1 to 10 MPa.

[0049]FIG. 4 is a schematic view illustrating the state of the interfacebetween a base material 1 and a resin layer 4 in a laminate which isproduced by using a prepreg produced by the method of the presentinvention, particularly a prepreg produced by using athree-dimensionally crosslinked silicone oligomer containingtrifunctional siloxane units and/or tetrafunctional siloxane units. Thethree-dimensionally crosslinked silicone oligomer 8 is chemicallyadsorbed uniformly on the surface of the base material 1 to coat thebase material surface completely, and cushions the distortion on theinterface between the base material and the resin layer, to allow theresin to exhibit its excellent adhering function.

[0050] Method of producing resin varnishes for printed wiring boards

[0051] In the method of producing resin varnishes for printed wiringboard according to the present invention, after an inorganic filler isdipped for surface treatment in a treating liquid which comprises asolution of a silicone oligomer containing at least one kind of siloxaneunits selected from trifunctional siloxane units (Rsio_(3/2)) andtetrafunctional siloxane units (SiO_(4/2)), wherein each R is an organicgroup and the organic groups R in the silicone oligomer are identicalwith or different from one another, having a polymerization degree of 2to 70, and having at least one functional end group reactive to ahydroxyl group, a resin material is directly compounded with thetreating liquid containing the treated inorganic filler.

[0052] Generally, the silicone oligomers which may be used in thismethod are three-dimensionally crosslinked silicone oligomers. Forexample, preferred silicone oligomers comprise only trifunctionalsiloxane units, or only tetrafunctional siloxane units, or difunctionalsiloxane units and trifunctional siloxane units, or difunctionalsiloxane units and tetrafunctional siloxane units, or trifunctionalsiloxane units and tetrafunctional siloxane units, or difunctionalsiloxane units, trifunctional siloxane units and tetrafunctionalsiloxane units. Further, tetrafunctional siloxane units are preferably15 mol % or more, more preferably 20 to 60 mol %, based on totalsiloxane units. To coat the inorganic filler surface with a highlythree-dimensionally crosslinked layer, it is preferable to use siliconeoligomers containing trifunctional siloxane units and/or tetrafunctionalsiloxane units and having a polymerization degree of 6 to 70, morepreferably 10 to 50.

[0053] In the method of present invention, conventional coupling agentsmay also be used as surface treating agents together with the siliconeoligomers. Such coupling agents are, for example, silane coupling agentsand titanate coupling agents. Some examples of the silane couplingagents which may be used include epoxysilane coupling agents, such asγ-glycidoxypropyltrimethoxysilane, aminosilane coupling agents, such asN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride,cationic silane coupling agents, vinylsilane coupling agents,acrylsilane coupling agents, mercaptosilane coupling agents, andmixtures thereof. An example of the titanate coupling agents isisopropyltris(dioctylpyrophosphate) titanate. These may be usedindividually or in a combination of two or more in desired ratios.

[0054] In cases where such coupling agents are used together with thesilicone oligomers, the weight ratio of coupling agent:silicone oligomeris not particularly limited, and, to make both fully exhibit theirrespective properties, is desirably 0.001:1 to 1:0.001, preferably0.001:1 to 1:1.

[0055] The above-described direct compounding method is also effectiveto some degree in improving the dispersibility of inorganic fillerstreated with conventional coupling agents alone.

[0056] Solvents which may be used to prepare the treating liquid are notparticularly limited, and some examples include alcohols, such asmethanol and ethanol, ethers, such as ethylene glycol monomethyl ether,ketones, such as acetone, methyl ethyl ketone and methyl isobutylketone, amides, such as N,N-dimethylformamide, aromatic hydrocarbons,such as toluene and xylene, ethers, such as ethyl acetate, nitrites andwater, which may be used individually or as a solvent mixture of two ormore. The solid concentration in the treating liquid is not particularlylimited and may be varied depending on the kinds of the surface treatingagents used and on the desired adhesion amount of inorganic fillers.Generally, a suitable solid concentration is 0.1 to 50% by weight,preferably 0.1 to 20% by weight. If the solid concentration is less than0.1% by weight, the surface-treatment may take little recognizableeffect, and a solid concentration of more than 50% by weight may inducea deterioration in heat resistance or the like.

[0057] Inorganic fillers which may be used in the present invention arenot limited, and non-limitative and preferred examples are asexemplified above.

[0058] The method of the present invention is characterized in thatafter inorganic fillers are treated in a treating liquid, no drying iscarried out, but resin materials are compounded directly with thetreating liquid to produce a resin varnish. The temperature and time ofthe surface-treatment is not limited and may be varied depending on thekinds of the inorganic fillers and the surface treating agents used. Itis generally suitable to carry out the treatment at a temperatureranging from room temperature to 80° C. for 30 minutes or more,preferably 30 to 120 minutes.

[0059] Resin materials which may be used in the present invention arenot particularly limited, and resin materials which comprise the resinsor the resins and the curing agents as exemplified above are generallyused. The resins may be used individually or as a mixture of two ormore, and, according to demands, cure accelerators may also be addedthereto. A resin material comprising these components is directlycompounded with and dissolved into the treating liquid containing thetreated inorganic fillers.

[0060] Cure accelerators may be selected from known ones, and thepreferred examples are as exemplified above. The ratios of the resins,inorganic fillers, curing agents and cure accelerators in resinvarnishes are also as described above.

[0061] At the time of compounding resin materials with the treatingliquids to produce resin varnishes, solvents may further be added tocontrol the non-volatile solid concentration. The solvents are notlimited, and some examples are acetone, methyl ethyl ketone, toluene,xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycolmonomethyl ether, N,N-dimethylformamide, methanol and ethanol, which maybe used individually or as a mixture of two or more. The amount of theadditional solvents is not particularly limited, and is preferably suchthat the non-volatile solid concentration is 20 to 90% by weight, morepreferably 50 to 80% by weight.

[0062] According to the method of the present invention where resinvarnishes are produced by directly compounding a resin material with atreating liquid in which inorganic fillers were treated and are keptstay without separation nor drying, the inorganic fillers do not coherebut disperse uniformly in resin varnishes, so that the layer of thesurface treating agents are maintained uniform on the inorganic fillersurfaces. Since the compatibility of the surface treated inorganicfillers with resins is also improved, the blending amount of inorganicfillers can be increased. Further, this method is free from theformation of physically adsorbed layers which are formed by theoligomerization of conventional coupling agents and adversely affect theinterfacial adhesion, and is also free from the uneven surface treatmentlayers. Further, prepregs with good appearance can be obtained since theprecipitation of inorganic fillers in varnish tanks, etc. or adhesionthereof to rolls are prevented effectively. When used for the productionof laminates, the resin varnishes produced by this method improve theinterfacial adhesion in the laminates, and give laminates which areexcellent in drilling processability and insulation properties,including electrolytic corrosion. The inorganic filler/resin interfacesin the laminates produced by using the resin varnishes are also in thestate as shown in FIG. 4.

[0063] Laminates (b) for printed wiring boards

[0064] The laminate (b) of the present invention is useful for theproduction of printed wiring boards and is produced by impregnating abase material with a resin varnish for printed wiring boards produced bythe above-described method and drying the impregnated base material toform a prepreg, superposing two or more sheets of the, with a metal foilsuperposed on one or both sides of the superposed sheets of the prepreg,to form a superposed composite, and then bonding the superposedcomposite with heat and pressure.

[0065] The method of impregnating the base material with the resinvarnish is not particularly limited, and, for example, dipping, coatingor spraying is suitable. The base material may be selected withoutlimitation from those commonly used for the production of metal-cladlaminates or multilayer printed wiring boards, and suitable examples areas exemplified above. Woven or non-woven fabric of glass fiber ispreferable.

[0066] The base material impregnated with the resin varnish is thendried, for example, in a drying furnace, at 80 to 200° C., preferably100 to 180° C., for 3 to 30 minutes, preferably 5 to 15 minutes, to forma prepreg.

[0067] Plural sheets of the prepreg are superposed on each other, withmetal foil superposed on one or both sides of the superposed prepreg,and then bonded with heat and pressure, to produce the single-sided ordouble-sided metal-clad laminate (b) of the present invention. Thebonding step is generally carried out at 150 to 200° C., at a pressureof 1 to 10 MPa, for 30 to 150 minutes.

[0068] Resin compositions (A) for printed wiring boards

[0069] The resin composition (A) of the present invention is useful forthe production of printed wiring boards and comprises a resin materialand a silicone oligomer which contains at least one kind of siloxaneunits selected from trifunctional siloxane units (RSiO_(3/2)) andtetrafunctional siloxane units (SiO_(4/2)), wherein each R is an organicgroup and the organic groups R in the silicone oligomer are identicalwith or different from one another, has a polymerization degree of 2 to70, and has at least one functional end group reactive to a hydroxylgroup.

[0070] Resin materials which may be used in the present inventiongenerally comprises resins or resins and curing agents therefor. Theresins are not particularly limited, and the resins as exemplified aboveare generally used, and the curing agents as exemplified above aregenerally used. Cure accelerators may also be incorporated according todemands. Examples of the cure accelerators are as exemplified above. Theamounts of curing agents and cure accelerators depend on, for example,the combination of those and resins. The desirable blending ratios areas described above.

[0071] Generally, the resin compositions (A) of the present inventioncontain three-dimensionally crosslinked silicone oligomers.

[0072] For example, preferred silicone oligomers comprise onlytrifunctional siloxane units, or only tetrafunctional siloxane units, ordifunctional siloxane units and trifunctional siloxane units, ordifunctional siloxane units and tetrafunctional siloxane units, ortrifunctional siloxane units and tetrafunctional siloxane units, ordifunctional siloxane units, trifunctional siloxane units andtetrafunctional siloxane units. Further, tetrafunctional siloxane unitsare preferably 15 mol % or more, more preferably 20 to 60 mol %, basedon total siloxane units. To coat the base material surface with a highlythree-dimensionally crosslinked layer, it is preferable to use siliconeoligomers which contain trifunctional siloxane units and/ortetrafunctional siloxane units, and have a polymerization degree of 6 to70, more preferably 10 to 50. Silicone oligomers with polymerizationdegrees of higher than 70 may form uneven layers on the base materialsurface.

[0073] The amount of the silicone oligomers is not particularly limited,and is preferably 0.1 to 50 parts by weight, more preferably 0.1 to 20parts by weight, per 100 parts by weight of the resins. If the amount ofsilicone oligomers is less than 0.1 part by weight, the improvement ininterfacial adhesion may be insufficient, and if it is more than 50parts by weight, there may occur an decrease in heat resistance.

[0074] In addition to the silicone oligomers, additives, such as variouscoupling agents, may also be blended. Suitable coupling agents are, forexample, the silane coupling agents and titanate coupling agentsexemplified above. The amount of such coupling agents, if any, is notparticularly limited, and is generally 0.001 to 50 parts by weight,preferably 0.001 to 20 parts by weight, per 100 parts by weight of theresins.

[0075] The resin compositions (A) of the present invention may furthercontain inorganic fillers. Inorganic fillers which may be used are notparticularly limited, and examples are as exemplified above. The amountof the inorganic fillers are not particularly limited, and preferredamount is as disclosed above.

[0076] The resin compositions (A) of the present invention may be usedin various forms, and when used as resin varnishes for coating orimpregnating base materials, it may be used as diluted solutionsdissolved in solvents. The solvents are not limited, and some examplesare acetone, methyl ethyl ketone, toluene, xylene, methyl isobutylketone, ethyl acetate, ethylene glycol monomethyl ether,N,N-dimethylformamide, methanol, ethanol and water, which may be usedindividually or as a mixture of two or more. The amount of the solventsis not particularly limited, and is preferably such that thenon-volatile solid concentration is 20 to 90% by weight, more preferably50 to 80% by weight.

[0077] Laminates (c) for printed wiring boards

[0078] The laminate (c) of the present invention is useful for theproduction of printed wiring boards and is produced by impregnating abase material with the resin composition (A) and drying the impregnatedbase material to form a prepreg, superposing two or more sheets of theprepreg, with a metal foil superposed on one or both sides of thesuperposed sheets of the prepreg, to form a superposed composite, andthen bonding the superposed composite with heat and pressure.

[0079] The method of impregnating base materials with the resincomposition (A) is not particularly limited. For example, solvents andother additives are added according to demands to produce a resinvarnish, and a base material is impregnated with the resin varnish bydipping, coating or spraying. The base material may be selected withoutlimitation from those commonly used for the production of metal-cladlaminates or multilayer printed wiring boards, and suitable examples areas exemplified above. Woven or non-woven fabric of glass fiber ispreferable.

[0080] The base material impregnated with the resin varnish is thendried, for example, in a drying furnace, at 80 to 200° C. (in caseswhere solvents are used, at a temperature not lower than the temperatureat which the solvents can evaporate), preferably 100 to 180° C., for 3to 30 minutes, preferably 5 to 15 minutes, to form prepreg.

[0081] Plural sheets of the resulting prepreg are superposed on eachother, with metal foil superposed on one or both sides of the superposedprepreg, and then bonded with heat and pressure, to produce thesingle-sided or double-sided metal-clad laminate (c) of the presentinvention. The bonding step is generally carried out at 150 to 200° C.,at a pressure of 1 to 10 MPa, for 30 to 150 minutes.

[0082] The resin compositions (A) of the present invention contain athree-dimensionally crosslinked silicone oligomer having functional endgroups reactive to the hydroxyl groups on the surfaces of base materialsand inorganic fillers. Therefore, the layers of surface treating agentsformed on the base material/resin interface and on the inorganicfiller/resin interface are not such a thin and rigid layer as thatformed by conventional silane coupling agents or the like, but rathercushioning layers of the crosslinked silicone oligomer, which relievethe distortion occurring on the interfaces and allow resins to fullyexhibit their excellent adhesion function. The laminates and multilayerprinted wiring boards produced by using the resin compositions (A) ofthe present invention, therefore, are excellent in drillingprocessability and insulation properties.

[0083] The base material/resin interface and the inorganic filler/resininterface in the laminates produced by using the resin compositions (A)are also in the state as shown in FIG. 4.

[0084] Resin compositions (B) for printed wiring boards

[0085] The resin composition (B) of the present invention is useful forthe production of printed wiring boards and contains a resin materialand an inorganic filler as essential components, and is characterized inthat the inorganic filler has been pretreated with a silicone oligomerwhich contains at least one kind of siloxane units selected fromtrifunctional siloxane units (RSiO_(3/2)) and tetrafunctional siloxaneunits (SiO_(4/2)), wherein each R is an organic group and the organicgroups R in the silicone oligomer are identical with or different fromone another, has a polymerization degree of 2 to 70, and has at leastone functional end group reactive to a hydroxyl group.

[0086] Generally, the above-described silicone oligomer is athree-dimensionally crosslinked silicone oligomer. For example,preferred silicone oligomers comprise only trifunctional siloxane units,or only tetrafunctional siloxane units, or difunctional siloxane unitsand trifunctional siloxane units, or difunctional siloxane units andtetrafunctional siloxane units, or trifunctional siloxane units andtetrafunctional siloxane units, or difunctional siloxane units,trifunctional siloxane units and tetrafunctional siloxane units.Further, tetrafunctional siloxane units are preferably 15 mol % or more,more preferably 20 to 60 mol %, based on total siloxane units. To coatthe surfaces of inorganic fillers with a highly three-dimensionallycrosslinked layer, it is preferable to use silicone oligomers whichcontain trifunctional siloxane units and/or tetrafunctional siloxaneunits, have a polymerization degree of 6 to 70, more preferably 10 to50. Silicone oligomers with polymerization degrees of higher than 70 mayform uneven layer on the inorganic filler surface.

[0087] Inorganic fillers which may be used in the present invention arenot limited, and preferred examples are as exemplified above. Theseinorganic fillers may be used individually or as a mixture of two ormore of desired ratios.

[0088] The method of treating inorganic fillers with the siliconeoligomers is not particularly limited, and suitable methods are, forexample, dry methods where the silicone oligomer is directly added tothe inorganic filler, and a wet method where a diluted solution of thesilicone oligomer is used. The adhesion amount of the silicone oligomersto inorganic fillers is not particularly limited, and a suitableadhesion amount is generally 0.01 to 5% by weight, preferably 0.01 to2.00% by weight, based on the weight of the inorganic fillers. If it isless than 0.01% by weight, the effect of improving interfacial adhesionmay be insufficient, and if it is more than 5% by weight, there mayoccur a decrease in heat resistance.

[0089] The surface-treatment may also be carried out by using additives,including various coupling agents, together with the silicone oligomers.Suitable coupling agents are, for example, the silane coupling agentsand titanate coupling agents which were exemplified above. The additivesmay be used individually or in combination of two or more of desiredratios. The amount of the coupling agents, if any, is preferably suchthat the weight ratio of coupling agent:silicone oligomer is 0.001:1 to1:0.001, preferably 0.001:1 to 1:1.

[0090] In cases where the surface-treatment is carried out by a wetmethod using a diluted solution, suitable solvents are, for example,alcohols, such as methanol and ethanol, ethers, such as ethylene glycolmonomethyl ether, ketones, such as acetone, methyl ethyl ketone andmethyl isobutyl ketone, amides, such as N,N-dimethylformamide, aromatichydrocarbons, such as toluene and xylene, ethers, such as ethyl acetate,nitrites and water. The amount of solvents, if any, is not particularlylimited, and is preferably such that the concentration of non-volatilesolids, including the silicone oligomers, is 0.01 to 50% by weight, morepreferably 0.05 to 10% by weight. After the silicone oligomers and theoptional coupling agents adhered to the surfaces of inorganic fillers bythe dry or wet method, drying with heat is generally carried out at 50to 200° C., preferably 80 to 150° C., for 5 to 60 minutes, preferably 10to 30 minutes.

[0091] Resin materials which may be used in the present invention arenot particularly limited, and the resins as exemplified above aregenerally used, together with additives, such as curing agents and cureaccelerators, according to demands.

[0092] Suitable examples of the curing agents and cure accelerators arethe same as exemplified above, and these may also be used individuallyor as a mixture of two or more. The amounts of the curing agents and thecure accelerators depend, for example, on the combinations of the resinsand these agents. The preferred amounts are as described above.

[0093] In the resin composition (B) of the present invention, the ratioof the treated inorganic filler to the resin material is generally suchthat the treated inorganic filler is 1.0 to 500 parts by weight,preferably 10 to 100 parts by weight, per 100 parts by weight of theresins in the resin material.

[0094] The resin compositions (B) of the present invention may be usedin various forms, and when used as resin varnishes for coating orimpregnating base materials, they may be used as diluted solutionsdissolved in solvents.

[0095] Solvents which may be used are not limited, and some examples arealcohols, such as methanol and ethanol, ethers, such as ethylene glycolmonomethyl ether, ketones, such as acetone, methyl ethyl ketone andmethyl isobutyl ketone, amides, such as N,N-dimethylformamide, aromatichydrocarbons, such as toluene and xylene, ethers, such as ethyl acetate,and nitrites, which may be used individually or as a mixture of two ormore. The amount of the solvents is not particularly limited, and ispreferably such that the non-volatile solid concentration is 20 to 90%by weight, more preferably 50 to 80% by weight.

[0096] Laminates (d) for printed wiring boards

[0097] The laminate (d) of the present invention is useful for theproduction of printed wiring boards and is produced by impregnating abase material with the resin composition (B) and drying the impregnatedbase material to form a prepreg, superposing two or more sheets of theprepreg, with a metal foil superposed on one or both sides of thesuperposed sheets of the prepreg, to form a superposed composite, andthen bonding the superposed composite with heat and pressure.

[0098] The method of impregnating base materials with the resincomposition (B) is not particularly limited. For example, solvents andother additives are added according to demands to produce a resinvarnish, and a base material is impregnated with the resin varnish bydipping, coating or spraying. The base material may be selected withoutlimitation from those commonly used for the production of metal-cladlaminates or multilayer printed wiring boards, and suitable examples areas exemplified above. Woven or non-woven fabric of glass fiber ispreferable.

[0099] The base material impregnated with the resin varnish is thendried, for example, in a drying furnace, at 80 to 200° C., preferably100 to 180° C. (if solvents are used, at a temperature not lower thanthe temperature at which the solvents can evaporate), for 3 to 30minutes, preferably 5 to 15 minutes, to form a prepreg.

[0100] Plural sheets of the obtained prepreg are superposed on eachother, with metal foil superposed on one or both sides of the superposedprepreg, and then bonded with heat and pressure, to produce the laminate(d) of the present invention. When the metal foil is superposed on oneside, a single-sided metal-clad laminate is obtained, and when the metalfoil is superposed on both sides, a double-sided metal-clad laminate isobtained. The bonding step is generally carried out at 150 to 200° C.,at a pressure of 1 to 10 MPa, for 30 to 150 minutes.

[0101] The resin compositions (B) of the present invention contain athree-dimensionally crosslinked silicone oligomer having functional endgroups reactive to the hydroxyl groups on the surfaces of inorganicfillers. Therefore, the surface treating agent layer formed on theinorganic filler/resin interface is not such a thin and rigid layer asthat formed by conventional silane coupling agents or the like, butrather a cushioning layer of the crosslinked silicone oligomer, whichrelieves the distortion occurring on the interface and makes resinsfully exhibit their excellent adhesion function. The laminates andmultilayer printed wiring boards produced by using the resincompositions (B) of the present invention, therefore, are excellent indrilling processability and insulation properties.

[0102] The inorganic filler/resin interface in the laminates produced byusing the resin compositions (B) is also in the state as shown in FIG.4.

[0103] Hereinafter, the present invention will be described in detailreferring to working examples, which, however, do not limit the scope ofthe present invention.

(I) Examples of the method of producing prepregs for printed wiringboards and Examples of the laminate produced by using the prepregs, andComparative Examples Example I-1

[0104] To a glass flask equipped with a stirring apparatus, a condenserand a thermometer was introduced a solution of 40 g oftetramethoxysilane dissolved in 93 g of methanol, and after 0.47 g ofacetic acid and 18.9 g of distilled water were added thereto, themixture was then stirred at 50° C. for 8 hours, to synthesize a siliconeoligomer having a polymerization degree of 20 (conversion from theweight average molecular weight determined by GPC, and the same shallapply hereinafter) of siloxane units. The functional end groups of thesilicone oligomer, which are reactive to hydroxyl groups, are methoxygroups and/or silanol groups.

[0105] Methanol was added to the silicone oligomer, to prepare atreating liquid with a solid content of 1% by weight.

Example I-2

[0106] By using the same reactor as used in Example I-1, 0.53 g ofacetic acid and 15.8 g of distilled water were added to a solution of 40g of trimethoxymethylsilane dissolved in 93 g of methanol, and themixture was then stirred at 50° C. for 8 hours, to synthesize a siliconeoligomer having a polymerization degree of 15 of siloxane units. Thefunctional end groups of the silicone oligomer, which are reactive tohydroxyl groups, are methoxy groups and/or silanol groups.

[0107] Methanol was added to the silicone oligomer, to prepare atreating liquid with a solid content of 1% by weight.

Example I-3

[0108] By using the same reactor as used in Example I-1, 0.60 g ofacetic acid and 14.0 g of distilled water were added to a solution of 34g of dimethoxydimethylsilane and 8 g of tetramethoxysilane dissolved in98 g of methanol, and the mixture was then stirred at 50° C. for 8hours, to synthesize a silicone oligomer having a polymerization degreeof 28 of siloxane units. The functional end groups of the siliconeoligomer, which are reactive to hydroxyl groups, are methoxy groupsand/or silanol groups.

[0109] Methanol was added to the silicone oligomer, to prepare atreating liquid with a solid content of 1% by weight.

Example I-4

[0110] By using the same reactor as used in Example I-1, 0.60 g ofacetic acid and 17.8 g of distilled water were added to a solution of 20g of dimethoxydimethylsilane and 25 g of tetramethoxysilane dissolved in105 g of methanol, and the mixture was then stirred at 50° C. for 8hours, to synthesize a silicone oligomer having a polymerization degreeof 30 of siloxane units. The functional end groups of the siliconeoligomer, which are reactive to hydroxyl groups, are methoxy groupsand/or silanol groups.

[0111] Methanol was added to the silicone oligomer, to prepare atreating liquid with a solid content of 1% by weight.

Example I-5

[0112] By using the same reactor as used in Example I-1, 0.52 g ofacetic acid and 18.3 g of distilled water were added to a solution of 20g of trimethoxymethylsilane and 22 g of tetramethoxysilane dissolved in98 g of methanol, and the mixture was then stirred at 50° C. for 8hours, to synthesize a silicone oligomer having a polymerization degreeof 25 of siloxane units. The functional end groups of the siliconeoligomer, which are reactive to hydroxyl groups, are methoxy groupsand/or silanol groups.

[0113] Methanol was added to the silicone oligomer, to prepare atreating liquid with a solid content of 1% by weight.

Example I-6

[0114] By using the same reactor as used in Example I-1, 0.52 g ofacetic acid and 16.5 g of distilled water were added to a solution of 10g of dimethoxydimethylsilane, 10 g of trimethoxymethylsilane and 20 g oftetramethoxysilane dissolved in 93 g of methanol, and the mixture wasthen stirred at 50° C. for 8 hours, to synthesize a silicone oligomerhaving a polymerization degree of 23 of siloxane units. The functionalend groups of the siloxane oligomer, which are reactive to hydroxylgroups, are methoxy groups and/or silanol groups.

[0115] Methanol was added to the silicone oligomer, to prepare atreating liquid with a solid content of 1% by weight.

Example I-7

[0116] To the silicone oligomer solution obtained in Example I-4 wereadded γ-glycidoxypropyltrimethoxysilane (Trade name: A-187, produced byNippon Unicar Co., Ltd.), as a silane coupling agent, and methanol, toprepare a treating liquid with a solid content of 1% by weight (siliconeoligomer:A-187=1:0.5 weight ratio).

Example I-8

[0117] To the silicone oligomer solution obtained in Example I-4 wereaddedN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride(Trade name: SZ-6032, produced by Toray•Dow Corning•Silicone Co., Ltd.),as a silane coupling agent, and methanol, to prepare a treating liquidwith a solid content of 1% by weight (silicone oligomer:SZ-6032=1:0.5weight ratio).

[0118] A glass fabric of 0.2 mm thickness degreased by heating at 400°C. for 24 hours was dipped in each of the treating liquids obtained inExamples I-1 to 8, and was then dried by heating at 120° C. for 30minutes, to obtain a glass fabric the surface of which was coated with asilicone oligomer or a silicone oligomer/coupling agent mixture. Theadhesion amounts of the silicone oligomers in the treated glass fabricswere 0.08 to 0.11% by weight.

Example I-9

[0119] The glass fabric treated with the treating liquid of Example I-4(adhesion amount of silicone oligomer: 0.08% by weight) was furtherdipped in an aqueous solution containing 0.5% by weight ofγ-glycidoxypropyltrimethoxysilane (Trade name: A-187, produced by NipponUnicar Co., Ltd.), as a silane coupling agent, and 0.5% by weight ofacetic acid, and was then dried by heating at 120° C. for 30 minutes, toobtain a glass fabric the surface of which was treated with a siliconeoligomer and a silane coupling agent. The adhesion amount of the silanecoupling agent was 0.05% by weight.

Example I-10

[0120] The glass fabric treated with the treating liquid of Example I-4(adhesion amount of silicone oligomer: 0.08% by weight) was furtherdipped in an aqueous solution containing 0.5% by weight ofN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride(Trade name: SZ-6032, produced by Toray•Dow Corning•Silicone Co., Ltd.),as a silane coupling agent, and 0.5% by weight of acetic acid, and wasthen dried by heating at 120° C. for 30 minutes, to obtain a glassfabric the surface of which was treated with a silicone oligomer and asilane coupling agent. The adhesion amount of the silane coupling agentwas 0.04% by weight.

Example I-11

[0121] A glass fabric of 0.2 mm thickness degreased by heating at 400°C. for 24 hours was dipped in the aqueous solution which was the same asthat used in Example I-9 and contained γ-glycidoxypropyltrimethoxysilane(Trade name: A-187, produced by Nippon Unicar Co., Ltd.), as a silanecoupling agent, and was then dried by heating at 120° C. for 30 minutes,to obtain a glass fabric the surface of which was coated with thecoupling agent in an adhesion amount of 0.1% by weight. Thesurface-treated glass fabric was then dipped in the treating liquidproduced in Example 1-4, and dried by heating at 120° C. for 30 minutes,to obtain a glass fabric the surface of which was further coated withthe silicone oligomer. The adhesion amount of the silicone oligomer was0.04% by weight.

Example I-12

[0122] A glass fabric of 0.2 mm thickness degreased by heating at 400°C. for 24 hours was dipped in the aqueous solution which was the same asthat used in Example I-10 and containedN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride(Trade name: SZ-6032, produced by Toray•Dow Corning•Silicone Co., Ltd.),as a silane coupling agent, and was then dried by heating at 120° C. for30 minutes, to obtain a glass fabric the surface of which was coatedwith the coupling agent in an adhesion amount of 0.1% by weight. Thesurface-treated glass fabric was then dipped in the treating liquidproduced in Example I-4, and dried by heating at 120° C. for 30 minutes,to obtain a glass fabric the surface of which was further coated withthe silicone oligomer. The adhesion amount of the silicone oligomer was0.03% by weight.

Comparative Example I-1

[0123] As a glass fabric base material, the glass fabric of 0.2 mmthickness and with an adhesion amount ofγ-glycidoxypropyltrimethoxysilane (Trade name: A-187, produced by NipponUnicar Co., Ltd.) of 0.1% by weight, which was the same as that used inExample I-11, was used.

Comparative Example I-2

[0124] As a glass fabric base material, the glass fabric of 0.2 mmthickness and with an adhesion amount ofN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride(Trade name: SZ-6032, produced by Toray•Dow Corning•Silicone Co., Ltd.)of 0.1% by weight, which was the same as that used in Example I-12, wasused.

Comparative Example I-3

[0125] In place of a silicone oligomer treating liquid, a methanolsolution containing 1.0% by weight of an epoxy-modified silicone oil(Trade name: KF101, produced by Shin-Etsu Chemical Co., Ltd.) wasprepared as a treating liquid. A glass fabric of 0.2 mm thicknessdegreased by heating at 400° C. for 24 hours was dipped in the treatingliquid, and was then dried by heating at 120° C. for 30 minutes, toobtain a glass fabric the surface of which was coated with the siliconeoil. The adhesion amount of the silicone oil was 0.12% by weight.

[0126] The glass fabrics obtained in Examples I-1 to I-12 andComparative Examples I-1 to 3 were impregnated with the following epoxyresin varnish, and then dried by heating at 140° C. for 5 to 10 minutes,to obtain prepregs of a resinous solid content of 41% by weight. Foursheets of each prepreg were superposed on each other, with copper foilof 35 μm thickness superposed on each side of the superposed prepreg,and then bonding was performed under the pressing conditions of 170° C.,90 minutes and 4.0 MPa, to produce double-sided copper-clad laminates.

[0127] Brominated bisphenol A epoxy resin (epoxy equivalent weight:530): 100 parts by weight Dicyandiamide: 4 parts by weight2-ethyl-4-methylimidazole: 0.5 parts by weight

[0128] These compounds were dissolved in a solvent mixture of methylethyl ketone/ethylene glycol monomethyl ether (1/1 weight ratio), toprepare a resin varnish with a non-volatile solid content of 70% byweight, which was used as the above-described epoxy resin varnish.

[0129] The obtained double-sided copper-clad laminates were examined fordrilling processability, water absorption, soldering heat resistance andinsulation resistance. The results are listed in Table I-1. TABLE I-1Properties of laminates Drilling Insulation process- Water Solderingresistance (Ω) ability absorption heat Normal After (crack %) (wt %)resistance state 5-hr PCT Example No. I-1 20 0.72 OK 6.1 × 10¹⁵ 6.7 ×10¹³ I-2 25 0.70 OK 6.4 × 10¹⁵ 6.9 × 10¹³ I-3 27 0.70 OK 7.3 × 10¹⁵ 7.2× 10¹³ I-4 23 0.68 OK 7.0 × 10¹⁵ 6.9 × 10¹³ I-5 22 0.71 OK 6.2 × 10¹⁵7.0 × 10¹³ I-6 19 0.69 OK 6.9 × 10¹⁵ 7.3 × 10¹³ I-7 28 0.61 OK 7.1 ×10¹⁵ 7.1 × 10¹³ I-8 26 0.62 OK 7.2 × 10¹⁵ 7.2 × 10¹³ I-9 22 0.65 OK 7.5× 10¹⁵ 7.4 × 10¹³ I-10 21 0.66 OK 8.0 × 10¹⁵ 7.5 × 10¹³ I-11 30 0.70 OK6.8 × 10¹⁵ 7.0 × 10¹³ I-12 29 0.72 OK 7.0 × 10¹⁵ 7.1 × 10¹³ ComparativeExample No. I-1 48 0.69 OK 7.6 × 10¹⁵ 8.5 × 10¹² I-2 45 0.71 OK 8.1 ×10¹⁵ 1.5 × 10¹³ I-3 63 1.05 NG 5.5 × 10¹⁴ 5.5 × 10¹¹

[0130] Each test was carried out as follows. Except in the tests forelectrolytic corrosion resistance, test pieces from which copper foilwas completely etched off were used.

[0131] Drilling processability: After through holes were made by using adrill of φ0.4 mm at 80,000 r.p.m. and at a feed rate of 3,200 mm/min,the hole walls were examined for cracks which were made by, for example,the peeling on the base material/resin interfaces. The examination forthe cracks in the hole walls was carried out by boiling each drilledtest piece in a red checking liquid for an hour, microscopicallyobserving the wall surfaces, and determining the percentage of thesoaked area on the hole walls (average of the values of 20 holes). unit:%

[0132] Water absorption: was calculated from the difference between theweight at a normal state and the weight after a two-hours pressurecooker test (121° C., 2 atm). unit: % by weight

[0133] Soldering heat resistance: After a two-hours pressure cooker test(121° C., 2 atm), each test piece was dipped in a solder bath of 260° C.for 20 seconds, and its surfaces were visually observed. In the table,“OK” means the absence of measling or blistering.

[0134] Insulation resistance: Both at a normal state and after afive-hours pressure cooker test (121° C., 2 atm), each test piece wasapplied with a voltage of 500 V for one minute, and the insulationresistance was then measured. unit: Ω

[0135] As to Example I-1 and Comparative Example I-2, tests forelectrolytic corrosion resistance were carried out.

[0136] Electrolytic corrosion resistance: Each laminate was drilled byusing a drill of φ0.4 mm to make 300 through holes in total arranged sothat six lines each including 50 holes (pitch between holes: 1.0 mm)were lined in columns with a space of a hole pitch of 0.7 mm. Thethrough holes were copper-plated to 35 μm thickness by conventionalelectroless plating and electric plating. The laminate was then wired byphotolithography so that the 50 through holes in each line wereconnected in a form of connected cranks with lands of 0.6 mm diameterand connecting lines of 0.1 mm width. The wired lines were connectedalternately one another, and 100 V was applied at 85° C./85%RH by usingone group of the connected lines as anodes and the other group ascathodes.

[0137] In Comparative Example I-2, continuity breakdown due to CAF(Conductive Anodic Filament) took place about 1200 hours later, while inExample I-1, the insulation resistance was 10¹⁰ Ω or more even 1500hours later.

[0138] The results show that the copper-clad laminates obtained inExamples I-1 to 12 had sufficient soldering heat resistance, were hardlycracked by drilling, lost little insulation resistance by waterabsorption and had improved electrolytic corrosion resistance.

[0139] The prepregs for printed wiring boards produced by the method ofthe present invention can improve the laminates produced by using theprepregs in drilling processability and in insulation propertiesincluding electrolytic corrosion resistance, without deteriorating theproperties of the conventional laminates.

(II) Examples of the method of producing resin varnishes for printedwiring boards and laminates produced by using the resin varnish,Referential Examples and Comparative Examples Referential Example II-1

[0140] To a glass flask equipped with a stirring apparatus, a condenserand a thermometer were introduced γ-glycidoxypropyltrimethoxysilane(Trade name: A-187, produced by Nippon Unicar Co., Ltd.), as a silanecoupling agent, and methyl ethyl ketone, to produce a treating liquid ofa solid content of 10% by weight. Calcined clay (mean particle size: 1.2μm) was added to the treating liquid in an amount of 50% by weight basedon the resinous solid, and the mixture was then stirred for one hour atroom temperature, to produce a treating liquid containing asurface-treated inorganic filler.

Referential Example II-2

[0141] To a glass flask equipped with a stirring apparatus, a condenserand a thermometer were introducedN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride(Trade name: SZ-6032, produced by Toray•Dow Corning•Silicone Co., Ltd.),as a silane coupling agent, and methyl ethyl ketone, to produce atreating liquid of a solid content of 10% by weight. Calcined clay (meanparticle size: 1.2 μm) was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Referential Example II-3

[0142] To a glass flask equipped with a stirring apparatus, a condenserand a thermometer were introduced isopropyltris(dioctylpyrophosphate)titanate (Trade name: KR46B, produced by Ajinomoto Co., Ltd.), as atitanate coupling agent, and methyl ethyl ketone, to produce a treatingliquid of a solid content of 10% by weight. Calcined clay (mean particlesize: 1.2 μm) was added to the treating liquid in an amount of 50% byweight based on the resinous solid, and the mixture was then stirred forone hour at room temperature, to produce a treating liquid containing asurface-treated inorganic filler.

Example II-1

[0143] In a glass flask equipped with a stirring apparatus, a condenserand a thermometer was introduced a solution of 40 g oftetramethoxysilane dissolved in 93 g of methanol, and after 0.47 g ofacetic acid and 18.9 g of distilled water were added thereto, themixture was stirred for 8 hours at 50° C., to synthesize a siliconeoligomer having a polymerization degree of siloxane units of 20(conversion from the weight average molecular weight determined by GPC,and the same shall apply hereinafter). The functional end groups of thesilicone oligomer, which are reactive to hydroxyl groups, are methoxygroups and/or silanol groups.

[0144] Methyl ethyl ketone was added to the obtained silicone oligomersolution, to produce a treating liquid of a solid content of 10% byweight. Calcined clay was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Example II-2

[0145] By using the same reactor as used in Example II-1, 0.53 g ofacetic acid and 15.8 g of distilled water were added to a solution of 40g of trimethoxymethylsilane dissolved in 93 g of methanol, and themixture was then stirred for 8 hours at 50° C., to synthesize a siliconeoligomer having a polymerization degree of siloxane units of 15. Thefunctional end groups of the silicone oligomer, which are reactive tohydroxyl groups, are methoxy groups and/or silanol groups.

[0146] Methyl ethyl ketone was added to the obtained silicone oligomersolution, to produce a treating liquid of a solid content of 10% byweight. Calcined clay was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Example II-3

[0147] By using the same reactor as used in Example II-1, 0.60 g ofacetic acid and 14.0 g of distilled water were added to a solutioncontaining 34 g of dimethoxydimethylsilane and 8 g of tetramethoxysilanedissolved in 98 g of methanol, and the mixture was then stirred for 8hours at 50° C., to synthesize a silicone oligomer having apolymerization degree of siloxane units of 28. The functional end groupsof the silicone oligomer, which are reactive to hydroxyl groups, aremethoxy groups and/or silanol groups.

[0148] Methyl ethyl ketone was added to the obtained silicone oligomersolution, to produce a treating liquid of a solid content of 10% byweight. Calcined clay was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Example II-4

[0149] By using the same reactor as used in Example II-1, 0.60 g ofacetic acid and 17.8 g of distilled water were added to a solutioncontaining 20 g of dimethoxydimethylsilane and 25 g oftetramethoxysilane dissolved in 105 g of methanol, and the mixture wasthen stirred for 8 hours at 50° C., to synthesize a silicone oligomerhaving a polymerization degree of siloxane units of 30. The functionalend groups of the silicone oligomer, which are reactive to hydroxylgroups, are methoxy groups and/or silanol groups.

[0150] Methyl ethyl ketone was added to the obtained silicone oligomersolution, to produce a treating liquid of a solid content of 10% byweight. Calcined clay was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Example II-5

[0151] By using the same reactor as used in Example II-1, 0.52 g ofacetic acid and 18.3 g of distilled water were added to a solutioncontaining 20 g of trimethoxymethylsilane and 22 g of tetramethoxysilanedissolved in 98 g of methanol, and the mixture was then stirred for 8hours at 50° C., to synthesize a silicone oligomer having apolymerization degree of siloxane units of 25. The functional end groupsof the silicone oligomer, which are reactive to hydroxyl groups, aremethoxy groups and/or silanol groups.

[0152] Methyl ethyl ketone was added to the obtained silicone oligomersolution, to produce a treating liquid of a solid content of 10% byweight. Calcined clay was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Example II-6

[0153] By using the same reactor as used in Example II-1, 0.52 g ofacetic acid and 16.5 g of distilled water were added to a solutioncontaining 10 g of dimethoxydimethylsilane, 10 g oftrimethoxymethylsilane and 20 g of tetramethoxysilane dissolved in 93 gof methanol, and the mixture was then stirred for 8 hours at 50° C., tosynthesize a silicone oligomer having a polymerization degree ofsiloxane units of 23. The functional end groups of the siliconeoligomer, which are reactive to hydroxyl groups, are methoxy groupsand/or silanol groups.

[0154] Methyl ethyl ketone was added to the obtained silicone oligomersolution, to produce a treating liquid of a solid content of 10% byweight. Calcined clay was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Example II-7

[0155] By using the same reactor as used in Example II-1, 0.34 gof-acetic acid and 13.8 g of distilled water were added to a solutioncontaining 40 g of tetraethoxysilane dissolved in 93 g of methanol, andthe mixture was then stirred for 8 hours at 50° C., to synthesize asilicone oligomer having a polymerization degree of siloxane units of19. The functional end groups of the silicone oligomer, which arereactive to hydroxyl groups, are ethoxy groups and/or silanol groups.

[0156] Methyl ethyl ketone was added to the obtained silicone oligomersolution, to produce a treating liquid of a solid content of 10% byweight. Calcined clay was added to the treating liquid in an amount of50% by weight based on the resinous solid, and the mixture was thenstirred for one hour at room temperature, to produce a treating liquidcontaining a surface-treated inorganic filler.

Referential Example II-4

[0157] The procedure of Referential Example II-1 was repeated, exceptthat talc (mean particle size: 12 μm) was used as the inorganic filler,to produce a treating liquid containing a surface-treated inorganicfiller.

Referential Example II-5

[0158] The procedure of Referential Example II-1 was repeated, exceptthat silica (mean particle size: 1.0 μm) was used as the inorganicfiller, to produce a treating liquid containing a surface-treatedinorganic filler.

Example II-8

[0159] To the silicone oligomer solution obtained in Example II-1 wereadded γ-glycidoxypropyltrimethoxysilane (Trade name: A-187), as a silanecoupling agent, and methyl ethyl ketone, to produce a treating liquidhaving a solid content of 10% by weight (silicone oligomer:A-187=1:1weight ratio). Calcined clay was added to the treating liquid in anamount of 50% by weight based on the resinous solids, and the mixturewas stirred for one hour at room temperature, to obtain a treatingliquid containing a surface-treated inorganic filler.

Example II-9

[0160] To the silicone oligomer solution obtained in Example II-1 wereadded isopropyltris(dioctylpyrophosphate) titanate (Trade name: KR46B),as a titanate coupling agent, and methyl ethyl ketone, to produce atreating liquid having a solid content of 10% by weight (siliconeoligomer:KR46B=1:1 weight ratio). Calcined clay was added to thetreating liquid in an amount of 50% by weight based on the resinoussolids, and the mixture was stirred for one hour at room temperature, toobtain a treating liquid containing a surface-treated inorganic filler.

[0161] The treating liquids, which were obtained in Examples II-1 to 9and Referential Examples II-1 to 5 and contained surface-treatedinorganic fillers, were heated to 50° C., and the following resinmaterial and a solvent mixture of methyl ethyl ketone/ethylene glycolmonomethyl ether (1:1 weight ratio) were added thereto, to produce resinvarnishes of a solid content of 70% by weight.

[0162] Brominated bisphenol A epoxy resin (epoxy equivalent weight:530): 100 parts by weight Dicyandiamide: 4 parts by weight2-ethyl-4-methylimidazole: 0.5 parts by weight

Comparative Example II-1

[0163] Calcined clay, the surface of which had not been treated, wasmixed into a solvent mixture of methyl ethyl ketone/ethylene glycolmonomethyl ether (1:1 weight ratio) to a content of 50% by weight, andthe above-described resin material was then added thereto, to produce aresin varnish of a solid content of 70% by weight.

Comparative Example II-2

[0164] To 100 parts by weight of the resin varnish produced inComparative Example II-1 was added 2 parts by weight ofγ-glycidoxypropyltrimethoxysilane as a silane coupling agent.

Comparative Example II-3

[0165] A resin varnish was produced in the same manner as in ReferentialExample II-1, except that the calcined clay was treated with anepoxy-modified silicone oil (Trade name: KF101, produced by Shin-EtsuChemical Co., Ltd.) in place of the silane coupling agent.

Comparative Example II-4

[0166] The silane coupling agent used in Referential Example II-1,namely γ-glycidoxypropyltrimethoxysilane, was dissolved in methanol toproduce a treating liquid of a solid content of 1% by weight, whereincalcined clay the surface of which had not been treated was dipped forone hour with stirring and was then dried at 120° C. for one hour. Aresin varnish was produced in the same manner as in Comparative Example11-1, except that the treated, calcined clay was used.

[0167] A glass fabric of about 0.2 mm thickness was impregnated witheach of the resin varnishes produced in Examples II-1 to 9, ReferentialExamples II-1 to 5 and Comparative Examples II-1 to 4 to obtainimpregnated glass fabrics, which were then heated to 140° C. for 5 to 10minutes to dry, to obtain prepregs of a resin content of 41% by weight.Four sheets of each prepreg were superposed on each other, with copperfoil of 35 μm thickness superposed on each side of the superposedprepreg, and then bonding was performed under the pressing conditions of170° C., 90 minutes and 4.0 MPa, to produce double-sided copper-cladlaminates.

[0168] The obtained double-sided copper-clad laminates were examined fordrilling processability, water absorption, soldering heat resistance andelectrolytic corrosion resistance. The results are listed in Tables II-1and II-2. TABLE II-1 Referential Examples Examples II-1 II-2 II-3 II-1II-2 II-3 II-4 II-5 II-6 Coating NG NG NG Good Good Good Good Good Goodquality Appear- Good Good Good Good Good Good Good Good Good ance ofpre- preg Drilling 24 22 25 18 22 21 17 18 16 process- ability (crack %)Water 0.71 0.70 0.75 0.74 0.71 0.70 0.73 0.73 0.71 absorp- tion (wt %)Solder- OK OK OK OK OK OK OK OK OK ing heat resis- tanceElectro- >500 >500 >500 >500 >500 >500 >500 >500 >500 lytic cor- rosionresis- tance (hr)

[0169] TABLE II-2 Ex- am- ple Ref. Exs. Examples Comparative ExamplesII-7 II-4 II-5 II-8 II-9 II-1 II-2 II-3 II-4 Coating Good Good Good GoodGood NG NG NG NG quality Appear- Good Good Good Good Good NG NG NG NGance of pre- preg Drilling 19 23 24 23 23 38 37 40 36 process- ability(crack %) Water 0.70 0.74 0.73 0.69 0.68 0.88 0.88 0.95 0.80 absorp-tion (wt %) Solder- OK OK OK OK OK OK OK OK OK ing heat resis- tanceElectro- >500 >500 >500 >500 >500 288 288 216 360 lytic cor- rosionresis- tance (hr)

[0170] Each test was carried out as follows. The coating quality andappearance of the prepregs were evaluated previously by visualobservations. As to the coating quality, the prepregs which did notcause adhesion of inorganic fillers to rolls were rated as “Good”, andthe prepregs which caused such adhesion more or less as “NG”. As to theappearance of prepregs, prepregs which had the same even surfaces as ofthose containing no inorganic fillers were rated as “Good”, the othersas “NG”.

[0171] Except in the tests for electrolytic corrosion resistance, testpieces from which copper foil was completely etched off were used.

[0172] Drilling processability: After through holes were made by using adrill of φ0.4 mm at 80,000 r.p.m. and at a feed rate of 3,200 mm/min,the hole walls were examined for cracks which were made by, for example,the peeling on the base material/resin interfaces. The examination forthe cracks in the hole walls was carried out by boiling each drilledtest piece in a red checking liquid for an hour, microscopicallyobserving the wall surfaces, and determining the percentage of thesoaked area on the hole walls (average of 20 holes). unit: %

[0173] Water absorption: was calculated from the difference between theweight at a normal state and the weight after a two-hours pressurecooker test (121° C., 2 atm). unit: % by weight

[0174] Soldering heat resistance: After a two-hours pressure cooker test(121° C., 2 atm), each test piece was dipped in a solder bath of 260° C.for 20 seconds, and the surfaces thereof were visually observed. In thetable, “OK” means the absence of measling or blistering.

[0175] Electrolytic corrosion resistance: In the same manner asdescribed above, the time taken to cause continuity breakdown byapplication of 100 V at 85° C./85%RH was measured. Also, the continuitybreakdown was confirmed to be caused by the CAF (Conductive Anodicfilament) between through holes.

[0176] The results show that the prepregs of Examples II-1 to 9 andReferential Examples II-1 to 5 had good appearance, and the laminatesproduced by using these prepregs had sufficient soldering heatresistance, absorbed little water, were hardly cracked by drilling, andhad improved electrolytic corrosion resistance. Particularly, theprepregs produced in Examples II-1 to 9 caused no adhesion of inorganicfillers to rolls, and were particularly improved in coating quality.

[0177] The prepregs which are produced by using the resin varnishesproduced by the method of the present invention are excellent inappearance, and can improve the laminates produced by using them indrilling processability and in insulation properties includingelectrolytic corrosion resistance, without deteriorating the propertiesof the conventional laminates.

(III) Examples of resin compositions (A) for printed wiring boards andlaminates produced by using the resin compositions (A), and ComparativeExamples Example III-1

[0178] To a glass flask equipped with a stirring apparatus, a condenserand a thermometer was introduced a solution containing 40 g oftetramethoxysilane dissolved in 93 g of methanol, and after 0.47 g ofacetic acid and 18.9 g of distilled water were added thereto, themixture was stirred for 8 hours at 50° C., to synthesize a siliconeoligomer having a polymerization degree of siloxane units of 20(conversion from the weight average molecular weight determined by GPC,and the same shall apply hereinafter). The functional end groups of thesilicone oligomer, which are reactive to hydroxyl groups, are methoxygroups and/or silanol groups.

Example III-2

[0179] By using the same reactor as used in Example III-1, 0.53 g ofacetic acid and 15.8 g of distilled water were added to a solution of 40g of trimethoxymethylsilane dissolved in 93 g of methanol, and themixture was then stirred for 8 hours at 50° C., to synthesize a siliconeoligomer having a polymerization degree of siloxane units of 15. Thefunctional end groups of the silicone oligomer, which are reactive tohydroxyl groups, are methoxy groups and/or silanol groups.

Example III-3

[0180] By using the same reactor as used in Example III-1, 0.60 g ofacetic acid and 14.0 g of distilled water were added to a solutioncontaining 34 g of dimethoxydimethylsilane and 8 g of tetramethoxysilanedissolved in 98 g of methanol, and the mixture was then stirred for 8hours at 50° C., to synthesize a silicone oligomer having apolymerization degree of siloxane units of 28. The functional end groupsof the silicone oligomer, which are reactive to hydroxyl groups, aremethoxy groups and/or silanol groups.

Example III-4

[0181] By using the same reactor as used in Example III-1, 0.60 g ofacetic acid and 17.8 g of distilled water were added to a solutioncontaining 20 g of dimethoxydimethylsilane and 25 g oftetramethoxysilane dissolved in 105 g of methanol, and the mixture wasthen stirred for 8 hours at 50° C., to synthesize a silicone oligomerhaving a polymerization degree of siloxane units of 30. The functionalend groups of the silicone oligomer, which are reactive to hydroxylgroups, are methoxy groups and/or silanol groups.

Example III-5

[0182] By using the same reactor as used in Example III-1, 0.52 g ofacetic acid and 18.3 g of distilled water were added to a solutioncontaining 20 g of trimethoxymethylsilane and 22 g of tetramethoxysilanedissolved in 98 g of methanol, and the mixture was then stirred for 8hours at 50° C., to synthesize a silicone oligomer having apolymerization degree of siloxane units of 25. The functional end groupsof the silicone oligomer, which are reactive to hydroxyl groups, aremethoxy groups and/or silanol groups.

Example III-6

[0183] By using the same reactor as used in Example III-1, 0.52 g ofacetic acid and 16.5 g of distilled water were added to a solutioncontaining 10 g of dimethoxydimethylsilane, 10 g oftrimethoxymethylsilane and 20 g of tetramethoxysilane dissolved in 93 gof methanol, and the mixture was then stirred for 8 hours at 50° C., tosynthesize a silicone oligomer having a polymerization degree ofsiloxane units of 23. The functional end groups of the siliconeoligomer, which are reactive to hydroxyl groups, are methoxy groupsand/or silanol groups.

Example III-7

[0184] By using the same reactor as used in Example III-1, 0.34 g ofacetic acid and 13.8 g of distilled water were added to a solutioncontaining 40 g of tetraethoxysilane dissolved in 93 g of methanol, andthe mixture was then stirred for 8 hours at 50° C., to synthesize asilicone oligomer having a polymerization degree of siloxane units of19. The functional end groups of the silicone oligomer, which arereactive to hydroxyl groups, are ethoxy groups and/or silanol groups.

[0185] By using the silicone oligomers synthesized in Examples III-1 to7, epoxy resin varnishes containing the following components wereprepared.

[0186] Brominated bisphenol A epoxy resin (epoxy equivalent weight:530): 100 parts by weight Dicyandiamide: 4 parts by weight Siliconeoligomer: 2 parts by weight 2-ethyl-4-methylimidazole: 0.5 parts byweight

[0187] These compounds were dissolved in a methyl ethyl ketone/ethyleneglycol monomethyl ether (1:1 weight ratio) solvent mixture, to produceresin varnishes of a non-volatile solid content of 70% by weight.

Example III-8

[0188] A resin varnish was produced with the same ratios of thecomponents as described above, except that the amount of the siliconeoligomer of Example III-1 were changed to one part by weight, and onepart by weight of γ-glycidoxypropyltrimethoxysilane (Trade name: A-187,produced by Nippon Unicar Co., Ltd.), as a silane coupling agent, wasadded thereto to produce a resin varnish of a non-volatile solid contentof 70% by weight.

Example III-9

[0189] A resin varnish was produced with the same ratios of thecomponents as described above, except that the amount of the siliconeoligomer of Example III-1 were changed to one part by weight, and onepart by weight ofN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride(Trade:name: SZ-6032, produced by Toray•Dow Corning•Silicone Co., Ltd.),as a silane coupling agent, to produce a resin varnish of a non-volatilesolid content of 70% by weight.

Example III-10

[0190] To the resin varnish of Example III-1 containing 2 parts byweight of the silicone oligomer, was added calcined clay (mean particlesize: 1.2 μm) as an inorganic filler in an amount of 50 parts by weightper 100 parts by weight of the epoxy resin, to produce a resin varnishof a non-volatile solid content of 70% by weight.

Comparative Example III-1

[0191] A resin varnish was produced in the same manner as in ExamplesIII-1 to 7, except that no silicone oligomers were added.

Comparative Example III-2

[0192] A resin varnish was produced in the same manner as in ExamplesIII-1 to 7, except that 2 parts by weight ofγ-glycidoxypropyltrimethoxysilane was used in place of the siliconeoligomers.

Comparative Example III-3

[0193] A resin varnish was produced in the same manner as in ExamplesIII-1 to 7, except that 2 parts by weight of an epoxy-modified siliconeoil (Trade name: KF101, produced by Shin-Etsu Chemical Co., Ltd. wasused in place of the silicone oligomers.

Comparative Example III-4

[0194] A resin varnish was produced in the same manner as in ExampleIII-9, except that no silicone oligomers were used.

Comparative Example III-5

[0195] To the resin varnish of Comparative Example III-2 was addedcalcined clay as an inorganic filler in an amount of 50 parts by weightper 100 parts by weight of the epoxy resin, to produce a resin varnishof a non-volatile solid content of 70% by weight.

[0196] A glass fabric of about 0.2 mm thickness was impregnated witheach of the resin varnishes produced in Examples III-1 to 10 andComparative Examples III-1 to 5 to obtain impregnated glass fabrics,which were then heated to 140° C. for 5 to 10 minutes to dry, to obtainprepregs of a resin content of 41% by weight. Four sheets of eachprepreg were superposed on each other, with copper foil of 35 μmthickness superposed on each side of the superposed prepreg, and thenbonding was performed under the pressing conditions of 170° C., 90minutes and 4.0 MPa, to produce double-sided copper-clad laminates.

[0197] The obtained double-sided copper-clad laminates were examined fordrilling processability, water absorption, soldering heat resistance andelectrolytic corrosion resistance. The results are listed in TablesIII-1 and III-2. TABLE III-1 Examples III-1 III-2 III-3 III-4 III-5III-6 III-7 Dimethoxydimethyl- — — 34 20 — 10 — silane (g)Trimethoxymethyl- — 40 — — 20 10 — silane (g) Tetramethoxysilane (g) 40— 8 25 22 20 — Tetraethoxysilane (g) — — — — — — 40 Methanol (g) 93 9398 105 98 93 93 Acetic acid (g) 0.47 0.53 0.60 0.60 0.52 0.52 0.34Distilled water (g) 18.9 15.8 14.0 17.8 18.3 16.5 13.8 Conditions of 50°C., 8 hours synthesis Siloxane repeating 20 15 28 30 25 23 19 unitsEpoxy resin (wt parts) 100 100 100 100 100 100 100 Silicone oligomer (wt2 2 2 2 2 2 2 parts) A-187 (wt parts) — — — — — — — SZ-6032 (wt parts) —— — — — — — Epoxy-modified — — — — — — — silicone oil (wt parts)Calcined Clay (wt — — — — — — — parts) Drilling process- 22 26 25 21 2220 23 ability (crack %) Water absorption 0.71 0.68 0.67 0.70 0.71 0.680.73 (wt %) Soldering heat OK OK OK OK OK OK OK resistance Electrolyticcorrosion >500 >500 >500 >500 >500 >500 >500 resistance (hr)

[0198] TABLE III-2 Examples Comparative Examples III-8 III-9 III-10III-1 III-2 III-3 III-4 III-5 Epoxy resin 100 100 100 100 100 100 100100 (wt part) Silicone 1 1 2 — — — — — oligomer (Example III-1) (wtparts) A-187 (wt 1 — — — 2 — — 2 parts) SZ-6032 (wt — 1 — — — — 1 —parts) Epoxy- — — — — — 2 — — modified silicone oil (wt parts) Calcinedclay — — 50 — — — — 50 (wt part) Drilling 28 25 19 43 41 48 38 37processability (crack %) Water absorp- 0.63 0.62 0.75 0.70 0.69 0.751.05 0.88 tion (wt %) Soldering heat OK OK OK OK OK OK OK OK resistanceElectrolytic >500 >500 >500 360 336 315 192 288 corrosion resistance(hr)

[0199] The tests were carried out in the same manner as in Examples II-1to 9, Referential Examples II-1 to 5 and Comparative Examples II-1 to 4.Except in the tests for electrolytic corrosion resistance, test piecesfrom which copper foil was completely etched off were used.

[0200] The results show that the laminates of Examples III-1 to 10 hadgood appearance, and the laminates produced by using these prepregs hadsufficient soldering heat resistance, were hardly cracked by drilling,and had improved electrolytic corrosion resistance.

[0201] The resin compositions (A) of the present invention can improvethe laminates produced by using them in drilling processability and ininsulation properties including electrolytic corrosion resistance,without deteriorating the properties of the conventional laminates.

(IV) Examples of resin compositions (B) for printed wiring boards andlaminates produced by using the resin compositions (B), and ComparativeExamples Example IV-1

[0202] To a glass flask equipped with a stirring apparatus, a condenserand a thermometer was introduced a solution containing 40 g oftetramethoxysilane dissolved in 93 g of methanol, and after 0.47 g ofacetic acid and 18.9 g of distilled water were added thereto, themixture was stirred for 8 hours at 50° C., to synthesize a siliconeoligomer having a polymerization degree of siloxane units of 20(conversion from the weight average molecular weight determined by GPC,and the same shall apply hereinafter). The functional end groups of thesilicone oligomer, which are reactive to hydroxyl groups, are methoxygroups and/or silanol groups.

[0203] Methanol was added to the obtained silicone oligomer solution, toproduce a treating liquid of a solid content of 1% by weight.

Example IV-2

[0204] By using the same reactor as used in Example IV-1, 0.53 g ofacetic acid and 15.8 g of distilled water were added to a solution of 40g of trimethoxymethylsilane dissolved in 93 g of methanol, and themixture was then stirred for 8 hours at 50° C., to synthesize a siliconeoligomer having a polymerization degree of siloxane units of 15. Thefunctional end groups of the silicone oligomer, which are reactive tohydroxyl groups, are methoxy groups and/or silanol groups.

[0205] Methanol was added to the obtained silicone oligomer solution, toproduce a treating liquid of a solid content of 1% by weight.

Example IV-3

[0206] By using the same reactor as used in Example IV-1, 0.60 g ofacetic acid and 14.0 g of distilled water were added to a solutioncontaining 34 g of dimethoxydimethylsilane and 8 g of tetramethoxysilanedissolved in 98 g of methanol, and the mixture was then stirred for 8hours at 50° C., to synthesize a silicone oligomer having apolymerization degree of siloxane units of 28. The functional end groupsof the silicone oligomer, which are reactive to hydroxyl groups, aremethoxy groups and/or silanol groups.

[0207] Methanol was added to the obtained silicone oligomer solution, toproduce a treating liquid of a solid content of 1% by weight.

Example IV-4

[0208] By using the same reactor as used in Example IV-1, 0.60 g ofacetic acid and 17.8 g of distilled water were added to a solutioncontaining 20 g of dimethoxydimethylsilane and 25 g oftetramethoxysilane dissolved in 105 g of methanol, and the mixture wasthen stirred for 8 hours at 50° C., to synthesize a silicone oligomerhaving a polymerization degree of siloxane units of 30. The functionalend groups of the silicone oligomer, which are reactive to hydroxylgroups, are methoxy groups and/or silanol groups.

[0209] Methanol was added to the obtained silicone oligomer solution, toproduce a treating liquid of a solid content of 1% by weight.

Example IV-5

[0210] By using the same reactor as used in Example IV-1, 0.52 g ofacetic acid and 18.3 g of distilled water were added to a solutioncontaining 20 g of trimethoxymethylsilane and 22 g of tetramethoxysilanedissolved in 98 g of methanol, and the mixture was then stirred for 8hours at 50° C., to synthesize a silicone oligomer having apolymerization degree of siloxane units of 25. The functional end groupsof the silicone oligomer, which are reactive to hydroxyl groups, aremethoxy groups and/or silanol groups.

[0211] Methanol was added to the obtained silicone oligomer solution, toproduce a treating liquid of a solid content of 1% by weight.

Example IV-6

[0212] By using the same reactor as used in Example IV-1, 0.52 g ofacetic acid and 16.5 g of distilled water were added to a solutioncontaining 10 g of dimethoxydimethylsilane, 10 g oftrimethoxymethylsilane and 20 g of tetramethoxysilane dissolved in 93 gof methanol, and the mixture was then stirred for 8 hours at 50° C., tosynthesize a silicone oligomer having a polymerization degree ofsiloxane units of 23. The functional end groups of the siliconeoligomer, which are reactive to hydroxyl groups, are methoxy groupsand/or silanol groups.

[0213] Methanol was added to the obtained silicone oligomer solution, toproduce a treating liquid of a solid content of 1% by weight.

Example IV-7

[0214] By using the same reactor as used in Example IV-1, 0.34 g ofacetic acid and 13.8 g of distilled water were added to a solutioncontaining 40 g of tetraethoxysilane dissolved in 93 g of methanol, andthe mixture was then stirred for 8 hours at 50° C., to synthesize asilicone oligomer having a polymerization degree of siloxane units of19. The functional end groups of the silicone oligomer, which arereactive to hydroxyl groups, are ethoxy groups and/or silanol groups.

[0215] Methanol was added to the obtained silicone oligomer solution, toproduce a treating liquid of a solid content of 1% by weight.

Example IV-8

[0216] To the silicone oligomer solution obtained in Example IV-4 wereadded γ-glycidoxypropyltrimethoxysilane (Trade name: A-187, produced byNippon Unicar Co., Ltd.), as a silane coupling agent, and methanol, toproduce a treating liquid of a solid content of 1% by weight (siliconeoligomer:A-187 1:1 weight ratio).

Example IV-9

[0217] To the silicone oligomer solution obtained in Example IV-4 wereaddedN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane•hydrochloride(Trade name: SZ-6032, produced by Toray•Dow Corning•Silicone Co., Ltd.),as a silane coupling agent, and methanol, to produce a treating liquidof a solid content of 1% by weight (silicone oligomer:SZ-6032=1:1 weightratio).

[0218] Calcined clay (mean particle size: 1.2 μm), as an inorganicfiller, was dipped in each of the treating liquids produced in ExamplesIV-1 to 9 for one hour with stirring, filtered, and heated to 120° C.for one hour to dry, to obtain inorganic fillers treated with siliconeoligomers. The adhesion amounts of the silicone oligomers were 0.08 to0.11% by weight.

Example IV-10

[0219] An inorganic filler treated with a silicone oligomer was preparedin the same manner as in Example IV-1, except that talc (mean particlesize: 12 μm) was used as the inorganic filler. The adhesion amount ofthe silicone oligomer was 0.10% by weight.

Example IV-11

[0220] An inorganic filler treated with a silicone oligomer was preparedin the same manner as in Example IV-1, except that silica (mean particlesize: 1.0 μm) was used as the inorganic filler. The adhesion amount ofthe silicone oligomer was 0.09% by weight.

Example IV-12

[0221] To calcined clay was directly dropped the silicone oligomersolution which was produced in Example IV-1 and was not further dilutedwith methanol (silicone oligomer:calcined clay=1.0:100 weight ratio),and the mixture was stirred sufficiently, and was then dried at 120° C.for one hour, to obtain an inorganic filler treated with the siliconeoligomer. The adhesion amount of the silicone oligomer was 0.05% byweight.

[0222] The surface-treated inorganic fillers produced in Examples IV-1to 12 were mixed, respectively, with the following resin components inthe following ratios, to prepare epoxy resin varnishes.

[0223] Brominated bisphenol A epoxy resin (epoxy equivalent weight:530): 100 parts by weight Dicyandiamide: 4 parts by weight Siliconeoligomer-treated inorganic filler: 50 parts by weight2-ethyl-4-methylimidazole: 0.5 parts by weight

[0224] These compounds were dissolved or dispersed in a methyl ethylketone/ethylene glycol monomethyl ether solvent mixture (1:1 weightratio), to produce resin varnishes of a non-volatile solid content of70% by weight.

Comparative Example IV-1

[0225] A resin varnish was produced in the same manner as above, exceptthat a calcined clay which had not been surface-treated was used as aninorganic filler.

Comparative Example IV-2

[0226] A calcined clay with an adhesion amount of a silane couplingagent of 0.07% by weight was prepared by usingγ-glycidoxypropyltrimethoxysilane (Trade name: A-187, produced by NipponUnicar Co., Ltd.) in place of a silicone oligomer-containing treatingliquid, and a resin varnish was produced in the same manner as above,except that the obtained, calcined clay was used.

Comparative Example IV-3

[0227] A calcined clay with an adhesion amount of a silicone oil of0.06% by weight was prepared by using an epoxy-modified silicone oil(Trade name: KF101, produced by Shin-Etsu Chemical Co., Ltd.) in placeof a silicone oligomer-containing treating liquid, and a resin varnishwas produced in the same manner as above, except that the obtained,calcined clay was used.

[0228] A glass fabric of about 0.2 mm thickness was impregnated witheach of the resin varnishes produced in Examples IV-1 to 12 andComparative Examples IV-1 to 3 to obtain impregnated glass fabrics,which were then heated to 140° C. for 5 to 10 minutes to dry, to obtainprepregs of a resin content of 41% by weight. Four sheets of eachprepreg were superposed on each other, with copper foil of 35 μmthickness superposed on each side of the superposed prepreg, and thenbonding was performed under the pressing conditions of 170° C., 90minutes and 4.0 MPa, to produce double-sided copper-clad laminates.

[0229] The obtained double-sided copper-clad laminates were examined fordrilling processability, water absorption, soldering heat resistance andelectrolytic corrosion resistance. The results are listed in Tables IV-1and IV-2. TABLE IV-1 Examples IV-1 IV-2 IV-3 IV-4 IV-5 IV-6 IV-7Dimethoxydimethyl- — — 34 20 — 10 — silane (g) Trimethoxymethyl- — 40 —— 20 10 — silane (g) Tetramethoxysilane (g) 40 — 8 25 22 20 —Tetraethoxysilane (g) — — — — — — 40 Methanol (g) 93 93 98 105 98 93 93Acetic acid (g) 0.47 0.53 0.60 0.60 0.52 0.52 0.34 Distilled water (g)18.9 15.8 14.0 17.8 18.3 16.5 13.8 Conditions of 50° C., 8 hourssynthesis Siloxane repeating 20 15 28 30 25 23 19 units Calcined clayUsed Used Used Used Used Used Used Drilling process- 19 23 22 18 19 1720 ability (crack %) Water absorption 0.75 0.72 0.71 0.74 0.74 0.72 0.70(wt %) Soldering heat OK OK OK OK OK OK OK resistance Electrolyticcorrosion >500 >500 >500 >500 >500 >500 >500 resistance (hr)

[0230] TABLE IV-2 Comparative Examples Examples IV-8 IV-9 IV-10 IV-11IV-12 IV-1 IV-2 IV-3 Silicone Used Used Used Used Used — — — oligomerExample No.: IV-4 IV-4 IV-1 IV-1 IV-1 A-187 Used — — — — — Used —SZ-6032 — Used — — — — — — KF101 — — — — — — — Used Calcined clay UsedUsed — — Used Used Used Used Talc — — Used — — — — — Silica — — — Used —— — — Drilling 24 24 18 19 24 38 36 44 processability Water absorp- 0.680.67 0.74 0.73 0.77 0.88 0.80 0.92 tion (wt %) Soldering heat OK OK OKOK OK OK OK OK resistance Electrolytic >500 >500 >500 >500 >500 288 360240 corrosion resistance (hr)

[0231] The tests were carried out in the same manner as in Examples II-1to 9, Referential Examples II-1 to 5 and Comparative Examples II-1 to 4.Except in the tests for electrolytic corrosion resistance, test piecesfrom which copper foil was completely etched off were used.

[0232] The results show that the laminates of Examples IV-1 to 12 didnot decreased in soldering heat resistance, absorbed little water, werehardly cracked by drilling and were improved in electrolytic corrosionresistance.

[0233] The resin compositions (B) of the present invention can improvethe laminates produced by using them in drilling processability and ininsulation properties including electrolytic corrosion resistance,without deteriorating the properties of the conventional laminates.

[0234] Industrial Applicability

[0235] The prepregs provided by the present invention are excellent inthe adhesion on the interface between base materials and resins. Theresin varnishes provided by the present invention are excellent in thedispersibility of inorganic fillers and in the adhesion on the interfacebetween inorganic fillers and resins. The resin compositions provided bythe present invention are also excellent in the dispersibility ofinorganic fillers and in the adhesion on the interfaces betweeninorganic fillers and resins and between base materials and resins. Theprepregs, resin varnishes and resin compositions which are provided bythe present invention are useful for the production of laminates forprinted wiring boards and multilayer printed wiring boards, and theproduct printed wiring boards and multilayer printed wiring boards areexcellent not only in heat resistance and moisture resistance, but alsoin drilling processability and insulation properties, includingelectrolytic corrosion resistance, and are therefore suitable as partsof various electric and electronic apparatuses.

What is claimed is:
 1. A method of producing prepreg for a printedwiring board, comprising treating a glass base material with a siliconeoligomer having at least one functional end group reactive to a hydroxylgroup, impregnating the treated base material with a resin varnish, anddrying the impregnated base material, wherein the silicone oligomer (a)contains at least one kind of siloxane units selected from trifunctionalsiloxane units (RSiO_(3/2)) and tetrafunctional siloxane units(RSiO_(4/2)) wherein each R is an alkyl group, an aryl group or a vinylgroup and the organic groups R in the silicone oligomer are identicalwith or different from each other, (b) is synthesized by allowing atleast one chlorosilane or alkoxysilane corresponding to the siloxaneunits to react in the presence of water and an acid catalyst, (c) isthree-dimensionally crosslinked, and (d) has a polymerization degree ofat most
 70. 2. The method of claim 1 , wherein the resin varnishcomprises a resin and a curing agent therefor, the resin being selectedform the group consisting of epoxy resin, polyimide resin, triazineresin, phenolic resin, melamine resin, polyester resin and modifiedresins of these resins.
 3. The method of claim 1 , wherein the siliconeoligomer has a polymerization degree of 2 to
 70. 4. The method of claim1 , wherein the silicone oligomer comprises difunctional siloxane units(R₂SiO_(2/2)) and tetrafunctional siloxane units (SiO_(4/2)) and haspolymerization degree of 6 to
 70. 5. The method of claim 1 , wherein thesilicone oligomer comprises trifunctional siloxane units (RSiO_(3/2))and tetrafunctional siloxane units (SiO_(4/2)) and has a polymerizationdegree of 6 to
 70. 6. The method of claim 1 , wherein the siliconeoligomer comprises difunctional siloxane units (R₂SiO_(2/2)) andtrifunctional siloxane units (RSiO_(3/2)) and has a polymerizationdegree of 6 to
 70. 7. The method of claim 1 , wherein the siliconeoligomer comprises difunctional siloxane units (RSiO_(3/2)),trifunctional siloxane units (RSiO_(3/2)) and tetrafunctional siloxaneunits (SiO_(4/2)) and has a polymerization degree of 6 to
 70. 8. Themethod of claim 7 , wherein the tetrafunctional siloxane units(SiO_(4/2)) are at least 15 mol % of total siloxane units of thesilicone oligomer.
 9. The method of claim 5 , wherein thetetrafunctional siloxane units (SiO_(4/2)) are at least 15 mol % oftotal siloxane units of the silicone oligomer.
 10. The method of claim 4, wherein the tetrafunctional siloxane units (SiO_(4/2)) are at least 15mol % of total siloxane units of the silicone oligomer.
 11. The methodof claim 1 , wherein the silicone oligomer comprises tetrafunctionalsiloxane units (SiO_(4/2)) and has a polymerization degree of 6 to 70.12. The method of claim 1 , wherein the silicone oligomer comprisestrifunctional siloxane units (RSiO_(3/2)) and has a polymerizationdegree of 6 to
 70. 13. The method of claim 1 , wherein the siliconeoligomer is used together with a silane coupling agent for treating thebase material.
 14. The method of claim 1 , wherein after the treatmentwith the silicone oligomer, the treated base material is further treatedwith a silane coupling agent.
 15. A laminate for a printed wiring board,which is produced by superposing two or more sheets of the prepregproduced by the method of claim 1 on each other, with a metal foilsuperposed on one or both sides of the superposed sheets of the prepreg,to form a superposed composite, and then bonding the superposedcomposite with heat and pressure.
 16. The method of claim 1 , whereinthe at least one functional end group reactive to a hydroxyl group isselected from the group consisting of alkoxyl groups of one or twocarbon atoms and silanol groups.
 17. A glass fiber base material treatedwith a silicone oligomer, wherein the silicone oligomer (a) contains atleast one kind of siloxane units selected from trifunctional siloxaneunits (RSiO_(3/2)) and tetrafunctional siloxane units (RSiO_(4/2)),wherein each R is an alkyl group, an aryl group or a vinyl group and theorganic groups R in the silicone oligomer are identical with ordifferent from each other, (b) is synthesized by allowing at least onechlorosilane or alkoxysilane corresponding to the siloxane units toreact in the presence of water and an acid catalyst, (c) isthree-dimensionally crosslinked, and (d) has a polymerization degree ofat most
 70. 18. The glass fiber base material of claim 17 , wherein thesilicone oligomer comprises difunctional siloxane units (R₂SiO_(2/2))and tetrafunctional siloxane units (SiO_(4/2)) and has a polymerizationdegree of 6 to
 70. 19. The glass fiber base material of claim 18 ,wherein the tetrafunctional siloxane units (SiO_(4/2)) are at least 15mol % of total siloxane units of the silicone oligomer.
 20. The glassfiber base material of claim 17 , wherein the silicone oligomercomprises trifunctional siloxane units (RSiO_(3/2)) and tetrafunctionalsiloxane units (SiO_(4/2)) and has a polymerization degree of 6 to 70.21. The glass fiber base material of claim 20 , wherein thetetrafunctional siloxane units (SiO_(4/2)) are at least 15 mol % oftotal siloxane units of the silicone oligomer.
 22. The glass fiber basematerial of claim 17 , wherein the silicone oligomer comprisesdifunctional siloxane units (R₂SiO_(2/2)) and trifunctional siloxaneunits (RSiO_(3/2)) and has a polymerization degree of 6 to
 70. 23. Theglass fiber base material of claim 17 , wherein the silicone oligomercomprises difunctional siloxane units (R₂SiO_(2/2)), trifunctionalsiloxane units (RSiO_(3/2)) and tetrafunctional siloxane units(SiO_(4/2)) and has a polymerization degree of 6 to
 70. 24. The glassfiber base material of claim 23 , wherein the tetrafunctional siloxaneunits (SiO_(4/2)) are at least 15 mol % of total siloxane units of thesilicone oligomer.
 25. The glass fiber base material of claim 17 ,wherein the silicone oligomer comprises tetrafunctional siloxane units(SiO_(4/2)) and has a polymerization degree of 6 to
 70. 26. The glassfiber base material of claim 25 , wherein the tetrafunctional siloxaneunits (SiO_(4/2)) are at least 15 mol % of total siloxane units of thesilicone oligomer.
 27. The glass fiber base material of claim 17 ,wherein the silicone oligomer comprises trifunctional siloxane units(RSiO_(3/2)) and has a polymerization degree of 6 to
 70. 28. The glassfiber base material of claim 17 , wherein the silicone oligomer is usedtogether with a silane coupling agent for treating the base material.29. The glass fiber base material of claim 17 , wherein after treatmentwith the silicone oligomer, the treated base material is further treatedwith a silane coupling agent.